It resets automatically after I installed and application and turned off the phone. It no longer stays on. It last like a 20-30 seconds and restarts twice, then the third time it goes off completely till i turn it on again and it repeats the process.

I would pull the battery out for about 10min. If you're not able to remove the battery I would find the reset key sequence to reset the phone.

1. Press and hold both the volume up key and the power
   key for five seconds.
2. After your phone vibrates once, release the keys. The phone restarts automatically

http://www.sonymobile.com/gb/support/faq/xperia-sola/troubleshooting/the-phone-freezes-or-applications-suddenly-shut-down-6/

Restart your phone by holding down your Home Button and your Lock Button at the same time for about 10 seconds or until you see the apple logo. This will restart your phone and should resolve your problem!

This problem cause due to over usage of phone memory.So, first of all try to remove sim card and charger and try to reboot the phone for 5-10 times.If the problem still persist contact mobile repairing shop or follow the steps below First download and install Pheonix from this link. Nokia Phoenix Service Software 2011 - Download secondly Download flash file from this link C 3 flash file and install it to C / program files/pheonix.. after finished this installation open pheonix . Inside the interface at the> top left <there you see "File" click there and choose "open file" and then select the approprait Product type i.e "which is written on the back panel inside the battery of every Nokia(Type RM-000).After doing this again at the left top count from "File"1..2..3..the 4th one is "Flashing" press there, when you click there you'll see three sub-menus, just select the "Firmware Update" again you'll see another interface. Look at the product code there should be blank and put your "mouse tool" at the straight end from the "Product Code" there is a Button and choose the code which is written in the back side of your phone. e.g CODE:0000000.if the same code does not found just take one which is higher. After this you can see "Dead phone USB flashing" click that box. Now this is the last stage... Connect your phone with the USB to your PC and let the driver install ...wait for a moment.(If your phone working).Lastly after just finished (In case your phone is Dead, unable to switch on in normal mode start from here) Connect the phone to pc without powering...insert good battery and Click the "Referbish" button after this, a message will prompt you "press power botton" etc. insert charger or press it and wait until the phone will Restart automatically in normal mode 10-15 minutes. If you cannot understand just leave a Comment / Click here1. thanks for visiting fixya. Good luck.

if you continously tried to install such applications your phone operating system may get damaged try to get certified applications from zedge.net

Please try resetting the phone.But please backup all the data because this process will erase everything.

CAUTION: If you have turned on encryption, the process for deleting all device data can take up to an hour to complete. You cannot stop the process after you start it. If you reset your device, the process restarts after the device restarts.

1. On the Home screen or in a folder, click the Options icon.
2. Click Security Options.
3. Click Security Wipe.
4. Perform any of the following actions:

• To delete data from the messages application, contacts application, and other applications, select the Emails, Contacts, Etc check box.
• To delete all third-party applications that you have added, select the User Installed Applications check box.
• To delete all files from your media card, select the Media Card check box.

5. Type blackberry.
6. Click Wipe.

format your phone
dial *#7370# and insert 12345 as phone code
your phone will formated

or use three finger method to format your phone
follow this instruction
Turns off the phone
Press simultaneously on the green/talk, 3 and* keys and hold the 3 keys.
Turn on your phone
Wait for the onscreen Format message then can release the three keys
This method may also work for Nokia phones that won't turn on.
Note that before making a reset on Nokia's latest phone
using the *#7370# or the 3 finger method, better make a backup, as you will automatically delete important data:
The license for pre-loaded contents (music, video, maps,etc..) and pre-installed application (N-gage)

Almost all cell phones have an option to reset to factory defaults.

You will loose ALL DATA!!

It is different for each phone but generally it is found under Settings -> Security -> Reset To Factory Settings

It may be called something different

Brother just hard reset»?

If something isn't working right, restarting, force quitting an application, or resetting
iPhone will likely solve the problem.
Restart iPhone: Press and hold the Sleep/Wake button until the red slider appears.
Slide your finger across the slider to turn off iPhone. To turn iPhone back on, press and
hold the Sleep/Wake until the Apple logo appears.
If you can't turn off iPhone or if the problem continues, you may need to reset. A reset
should be done only if turning iPhone off and on doesn't resolve the problem.
Force quit an application: Press and hold the Sleep/Wake button on top of iPhone
for a few seconds until a red slider appears, and then press and hold the Home button
until the application quits.
Reset iPhone: Press and hold the Sleep/Wake button and the Home button at the
same time for at least ten seconds, until the Apple logo appears.

did you try to reset the phone