Phone keeps locking itself
 

sorry i wanted to just edit my old thread and add this but it wouldn't edit.

But my phone while i am on it will randomly dim and then lock itself so i have to hit the unlock buttons on the screen. Any idea what might cause this? im using juicy 4.4 rom if that makes a difference. and i just got the phone and my friend flashed it to that so i can't say if it was doing it before. thanks and merry Christmas