This is usually caused by two major conditions.
The first condition being that if the Hard disk is really loaded with data and they are occupying a really large amount of the total disk space. This makes the console to have some kind of extra work to do while loading all the data which you have loaded onto it.
The second most known cause for this issue is as a result of errors in the hard disk or system. It makes it difficult for the system to operate as it should do normally.
Whatever the case may be, you can solve it by doing a hard reset on the PS3 console.
Below is the instruction on how to do a hard reset.
PS3 - How to do a factory / hard reset
Contributed by seamonkey420
April 9, 2007
Well, i had some major problems w/my PS3 recently locking up and
not playing any games/movies. After calling Customer Support, they
suggested that i do a hard reset. This did seem to solve my problems,
so here is the procedure per Sony CS. I would consider this a last
resort troubleshooting procedure.
Hard Reset procedure for the PS3 (as instructed by Sony CS).
Be sure to backup your settings/games saves by doing a System >
Backup on your PS3 or you may lose your game saves! Also, this is a
last resort procedure prior to exchanging/returning to sony.
1. Power Off the PS3 via the power switch in back and power back on w/switch.
2. Hold Power Button on the Front until you hear 3 beeps.
3. Then go through the initial setup and then run a full Format
via System > Format. (will take approx 3 1/1 hours). You may need
to have our AV cables ready if your using HDMI (in case HDMI isn't
detected after initial reset).
4. Restore your backup you made prior to doing factory/hard reset (optional, if you created a backup).
Hopefully this will solve your freezing problems.
Hope this solution was helpful? Please comment for more information and thank you for using fixya