I have a blackberry torch 9800 have had this phone for just over a year. The screen keeps freezing turning off and will not come back on till i pull the battery and then all is good for 2 minutes then it starts again.

What did you to the device just before this began to happen?

Have you let the battery run down past 20% more than a few times? If so, try a new OEM battery, not a cheap knock off.