When your PlayStation 3 freezes, generally there is little you can immediately do other than restart the console. Most freezes are infrequent errors, but chronic freezes may be the sign of an underlying issue. The best way to prevent future freezes is to discover and correct the cause. Common causes of freezes include system overheat, improperly installed or bugged updates and corrupt data.
Overheating is a frequent cause of PS3 freezes. Check your PS3's air vents for dust or clogs and regularly clean them using a microfiber cloth or a can of pressurized air. Also, check that there is sufficient space and airflow where your PS3 is stored; many entertainment centers feature spaces for devices but provide insufficient room to maintain airflow and a low operating temperature.
Update the Operating System
An incomplete or bugged update can also cause your PS3 to freeze or otherwise function incorrectly. You can install new updates via the setting's menu's System Update option, or using an update downloaded onto a USB storage device or installed on a game disc. Simply installing the newest update may correct the error causing the freezes.
Restore the File System
If corrupt data is the problem, you can restore the PS3's file system through Safe Mode and correct any damaged data. You can enter Safe Mode by shutting down the PS3, then starting it up by pressing and holding the power button for 10 seconds until you hear three beeps. It will shut down again, at which point you repeat the process until you hear a quick double-beep and see the Safe Mode screen appear. The option "Restore File System" will check your PS3's hard drive and repair any corrupted data, or delete any data that can't be repaired. This should fix any freezes related to bad or corrupted data.
Factory Reset the PS3
If all else fails to address the problem, you may need to restore your PS3 to factory settings. This option is available in both the system settings menu and Safe Mode, listed as "Restore PS3 System." This option will revert your system to its default settings, with no updates or additional settings. This option will delete all of your downloads and game save data, so it should only be used as a last resort.
Send Your Console for Service
If even a factory reset has not fixed the issue with freezing, your PS3's hardware may be defective or damaged. You'll have to either replace your PS3 or contact Sony for detailed troubleshooting instructions or the location of a licensed service center. The Resources section includes a link on how to send in your console for service or repair.