Odd behavior red and yellow led

My console plays fine I can watch Netflix etc watch dvds play cds all as per nomal and not be effected. The moment I put a game in and start playing the console shuts itself down after a brief green yellow led flash and then red continues to flash. Push power button twice and console cycles up again as though nothing happened. I changed the thermal paste this weekend this helped somewhat I played for nearly a hour before it bombed out. Turned it back on watched a full blueray movie then tried to game again. Got another hour and it died again. HELP!!!!