Points to either heat or hardware issues.
Start with a deep cleaning of vents, fans and heatsinks then leave the cover off for another test run.
Overclocking? You won't find me around PCs that do that. It's unsupportable and the owners tend to get this "entitled" view.
So i have a problem that my pc is shutting down when i play gta 5 or watch dogs 2, i can not turn it on unless is pull the plug out of my psu, pres the on button of my pc about 10 times and plug it back in. I play games like battlefield 1 and far cry 5 flawlessly on my pc and they stress my cpu and gpu more then gta5 and watch dogs2. I did overclock my cpu to 4.4 ghz and my gpu but i tried without any overclock and the same thing happend.
GTX970 MSI twinforzr
16gb ddr3 1333mhz
My temps are good, evrything sits below 65°C exept the gpu that likes to go up to 70°C with an overclok