Second night in a row this has happened; or every time I've played. After about 2 hours of play, the game locks for a second then my whole PC restarts - straight to POST. System is stable with other games / applications and I've thrown the book at it (i.e. if Star Citizen didn't tank it, then it's likely not hardware). The autosave from yesterday was corrupted when I hit continue.

Specs/details:
FX-8350 (barely OCed to 4.1, just because)
16 GB @ 1866MHz
ASUS Sabertooth 990FX r2.0
EVGA GTX 970 FTW ACX 2.0; left at factory OC
Soundblaster Z
Game is installed to an Intel 520 SSD, which is not the same disk as the OS' SSD
900W PCP&C power supply.
Win 8.1 Pro 64 bit
Running game at 1920x1080; however system res is set to 5760x1080
Using Xbox One controller
Settings at ultra / geralt only hairworks (getting a decent framerate - no stutter or lag; but guess I should have gone for SLI 980s to turn up the hirsute settings and skipped on getting a [now very dusty] PS4)
Launching game from Galaxy

Of the 'fixes' floating out there I have:
switched to borderless window
removed fps limit
set Nvidia control panel to max performance for TW3

Anyone else have this sort of issue? Bug or do I have some odd problem? Think it is related to the root of the general crashing issue (this is what I suspect personally, just getting hit harder for some reason)? This is helping me ration the game into short chunks and get some sleep, but come Friday, I'd like to binge.

Edit(s): Typos and left out info

Are you sure you're not overheating?

As a very general rule, if you break 90c on either your gpu or cpu it's running too hot. Even in the 80's it's hot, but I wouldn't expect a reboot from that.

I use HWINFO64 for hardware monitoring/logging but I think they're are other programs out there as well.

http://www.hwinfo.com/

A bios will typically force a system reset to protect your hardware when it gets too hot.

Was just trying to help. No offense intended.

Hard to determine tech level from a forum post. :)

Wasn't trying to be a jerk. It's just that PCs should have little Scotties (Star Trek, not dog) that yell 'That's all she's got, captain!" Long before anyone gets that hot. I know some people do inevitably wind up with heat issues, but they'd likely have run into issues much sooner. Thanks for the suggestion though; I'd already kept an eye on that this evening though, just in case something very strange was happening.