hey guys i am aslo facing the same prob for nearly a month

[tejas khandare]

my pc restart randomly only n only while playing games n while watching movies for 2 to 3 hrs i did prime 95 for 3 hrs no restart,n many more bt no restart at all,i had windows 10 os bt now i installed windows 8.1 os same prob yet my temps r low while playing games my cpu temps at 60 to 70 c n gpu goes to 80c max
my config
amd fx 8320
cm hyper212x cpu cooler
nvidia gtx 970 zotac
cosair 650w(dont know the model)
gigabyte 990fxa ud3

 

[Karadjgne]

3 things. Make sure the system is clean of dust/debris. Pay specific attention to the cpu/gpu heatsinks,
Check airflow. P95 does nothing for a gpu, and or case temps over and above what the cpu will exhaust, and both cpu and gpu should be running alot cooler. You may need to add/replace case fans to accomplish this.
Check fan curves. The 970 and up come with 0 rpm modes that don't turn on the gpu fans till they reach @62-65°. This is user changable, you can disable this setting and allow the gpu fans to spin up as normal. Cpu fan will always spin, but if the cpu is set to silent mode, you'll not see much in the way of cooling ability at higher temps as Intel/amd sees anything below @70° as nominal operating range. This can be changed either in bios or with motherboard software. Set fan curve to a more aggressive setting like performance or turbo mode. In bios, make sure cool'n'quiet is enabled