My specs are i7 6700k (OCed to 4.4ghz, CM 612 cooler), MSI Gaming X 1080 (384.94, but happened on previous version too).
It may sound like an overheating problem, but it shouldn't be. I've run some recodings with MSI afterburner and the temps were fine for most of the time (~58 max on the CPU, ~68 max on the GPU). Unfortunately restart corrupts the last data before it happens, so I can't tell exact temps at the point it restarts.
It's also irregular and seems to happen in specific places. For instance I've played for a few hours without a restart, but then I've entered Khartag Point and it restarted twice, I think.
So, what could it be?