My system turns off when i playing god of war 3 on ps3 it will shut of on me sometime?

my system turns off when i playing god of war 3 on ps3 it will shut of on me sometime for 1 hour r half and hour now 5 seconds once i log on it just turns off when i listenin to music r playing other games i dont have a problem it was a problem before but happens once a blue moon but now its been happening wne i play god of war 3 but mostly god of war its not ovber heating as i say once i log on sumtime it lastlong and sumtimes its for 5 seconds