I have an ipod classic 160Gb it is really slow, when I press any of the keys it takes ages to respond. sometimes it takes about 5 seconds to get back to the menu

The iPod is a portable music player made by Apple. As of early 2011, Apple sells four models: iPod shuffle, iPod classic, iPod nano and iPod touch. If your iPod experiences a problem such as not responding or freezing, you can reset it to see if that takes care of the problem. IPod Shuffle The iPod shuffle is the smallest iPod model, with 2GB of storage.
It has no screen and attaches to your clothing with a clip, making it well suited for exercising while listening to music.
When it doesn't respond, or if the status light is solid red, you can reset it.
Slide the three-way switch left toward the word "Off," covering the green bar. Wait 10 seconds, and then slide the switch back to reveal the green bar to turn it back on.
IPod Classic
The iPod classic has a 160GB hard drive for storing music, videos and pictures.
If it experiences a problem, you can easily reset it.
Slide the "Hold" switch to the "Hold" position and then slide it back.
Press "Menu" and the center button simultaneously on the click wheel and hold them for about six seconds, until Apple's logo appears on the screen.
IPod Nano
Apple's iPod nano has a touch-screen display and comes with 8GB or 16GB of storage, depending on the configuration.
It has a pedometer and an FM radio.
If the iPod nano doesn't respond, reset it.
Press the "Sleep/Wake" button and the "Volume Down" button simultaneously and hold them until the screen gets dark, and then wait a few more seconds until the Apple logo appears on the screen, followed by the home screen.
IPod Touch
The iPod touch has a touch-screen display, two cameras for shooting pictures and movies, and Wi-Fi for accessing the Internet. Its capacity ranges from 8GB to 64GB, depending on the configuration.
You can use the iPod touch to send email and make video calls, as well as play games and run applications. If the iPod touch freezes or otherwise isn't working, you can get it running again after resetting it.
Press the "On/Off-Sleep/Wake" button and the "Home" button simultaneously for at least 10 seconds, until Apple's logo appears on the screen.

The iPod is a portable music player made by Apple. As of early 2011, Apple sells four models: iPod shuffle, iPod classic, iPod nano and iPod touch. If your iPod experiences a problem such as not responding or freezing, you can reset it to see if that takes care of the problem. IPod Shuffle The iPod shuffle is the smallest iPod model, with 2GB of storage.
It has no screen and attaches to your clothing with a clip, making it well suited for exercising while listening to music.
When it doesn't respond, or if the status light is solid red, you can reset it.
Slide the three-way switch left toward the word "Off," covering the green bar. Wait 10 seconds, and then slide the switch back to reveal the green bar to turn it back on.
IPod Classic
The iPod classic has a 160GB hard drive for storing music, videos and pictures.
If it experiences a problem, you can easily reset it.
Slide the "Hold" switch to the "Hold" position and then slide it back.
Press "Menu" and the center button simultaneously on the click wheel and hold them for about six seconds, until Apple's logo appears on the screen.
IPod Nano
Apple's iPod nano has a touch-screen display and comes with 8GB or 16GB of storage, depending on the configuration.
It has a pedometer and an FM radio.
If the iPod nano doesn't respond, reset it.
Press the "Sleep/Wake" button and the "Volume Down" button simultaneously and hold them until the screen gets dark, and then wait a few more seconds until the Apple logo appears on the screen, followed by the home screen.
IPod Touch
The iPod touch has a touch-screen display, two cameras for shooting pictures and movies, and Wi-Fi for accessing the Internet. Its capacity ranges from 8GB to 64GB, depending on the configuration.
You can use the iPod touch to send email and make video calls, as well as play games and run applications. If the iPod touch freezes or otherwise isn't working, you can get it running again after resetting it.
Press the "On/Off-Sleep/Wake" button and the "Home" button simultaneously for at least 10 seconds, until Apple's logo appears on the screen.

See if this helps: http://support.apple.com/kb/TS1372

just do one thing Press Both menu and select buttons for few seconds till u see apple symbol on screen and leave it it will restore...!

Reset Click Wheel Ipod (newer ipods including resetting an ipod video)
1. Flip the Hold switch on and off and make sure it ends up no longer on hold.
2. Press and hold the Menu and Select buttons (center Button) until the Apple logo appears (may take 5-11 seconds, and you may need to repeat this step)
If this not work for you try plugging your ipod into computer or wall power


Resetting iPod (with dock connector)
Most problems with iPod can be solved by resetting it.
To reset iPod:
1 Connect iPod to a power outlet using the iPod Power Adapter.
2 Toggle the Hold switch on and off (set it to Hold, then turn it off again).
3 Press and hold the Play/Pause and Menu buttons for at least 5 seconds, until the
Apple logo appears.
If Your iPod Won't Turn On or Respond
* Make sure the Hold switch is off.
* If you're using the iPod Remote, make sure the remotes Hold switch is off.
* If that doesn't work, connect iPod to the iPod Power Adapter and connect the
adapter to a working electrical outlet. Your iPod battery may need to be recharged.


Resetting iPod (with out dock connector)
If that doesn't work, your iPod may need to be reset.While the iPod
is connected to power, press and hold the Play and Menu buttons
for at least 5 seconds, until the Apple logo appears.

Not sure what you meant by "restarted" but sometimes it takes "resetting" the ipod by plugging the cable into a reliable power source and then holding down both the menu and select (center circle) buttons for more than 5 seconds.

I am going to assume that it is your performance that is slowed down.
Unfortunately, there are not many ways to improve the performance, but there are plenty of ways to bog it down.
A way that I found (because I owned a 80 GB) was to NOT display the cover art/album art and disable the album art preview that appears on the right side of the screen when its at a menu.
For the iPod, loading a video will always be slow, but it holds steadily after. I heard it on my iPod a couple of times where the music will slow down (by only a few beats, but its noticeable), no idea why.
Do not load pictures on the iPod either, there really isn't a point.
Hope this helps.

My 80GB Ipod classic recently froze. I took it to Apple store and the guy press the Menu and Center Button. Hold them until the APPLE logo appears twice. Then release the button.
Voila, my Ipod work again, no missing data

Hi! YOu need to disconnect your ipod from the pc.
Put the ipod into diskmode by following these instructions-
Before placing the iPod into disk mode, you should verify that it is charged.
Toggle the Hold switch on and off. (Set it to Hold, then turn it off again.)
Press and hold the Menu and Select buttons for at least 6 seconds until the Apple logo appears.
When the Apple logo appears, release the Menu and Select buttons and immediately press and hold the Select and the Play/Pause buttons until the Disk Mode screen appears.
Connect the iPod to your computer; the screen on the iPod will change and say "Do not disconnect

After doing this open latest version of itunes and then restore your ipod to factory settings by selecting it from itunes.

I had the same problem. Try this: Toggle first Hold Button, push to Hold then leave it Unhold. Then long press Menu Button and the Center Button together for 10 seconds. Voila! There solves your problem.