COMPUTER SHUTS DOWN RANDOMLY WHEN PLAYING CERTAIN GAMES

[bloody actor]

MY gtx 970 was okay for certain months,but recently it started by refusing to display anything when i turned on my computer,I can clearly hear everything running but it wont display,the solution to this was sometimes leaving it off for a while or plug in a hdmi and it would turn on,then it started shutting down when playing certain games,my computer just shuts down when playing certain games or doing something heavy like 3d rendering,or video editing,I bought a new case and motherboard,but the problem off shutting down keeps reoccurring,what can i do guys,please help

[TheNuzziNuzz]

Does it blue screen or start shutting down as in "Windows is Shutting down" for a few seconds?

[Doramius]

If you haven't yet, try blowing out the dust from the heatsink.  It may still shut down, but if the time lengthens, you may need to reseat the heatsink with new thermal paste.  Could be something else, but this is an easy check.

[Tsuki]

specs?
temperatures?

 

could be thermal throttling, or possible psu going bad(less likely)

[benchmarker]

mostly power supply issue  

what are the specs?

[bloody actor]

it doesnt bluescreen,the thermals are usualy below 60 degrees,it began all this after installing a ups from mercury