!!! Screen crash !!!

Hi guys

I'm running Jellybam on my Note. Have had no problems previously. Lately, when i'm playing a game, the screen will start to flicker then the device shuts itself off.
I know this happens at low battery levels, however, this is happening when my phone is on full or near full charge. It's driving me crazy as I can't play any game for more than a few minutes at a time.
Anyone have any ideas as to what the problem is and any solution please?