I'm having the same issue...pretty disconcerting to get a hard reboot ever out of a game application.

i7 960 3.2ghz
gtx 970
32 GB RAM
SSD HDD
850w+ power supply

Haven't encountered this reset thing yet but I suggest opening up your pc case to help with the cooling if you are using stock gpu coolers.

Also may I suggest that you install the latest geforce drivers if you haven't done so.

As an alternative to the fan trick, I've also found that underclocking the card by 100MHz on GPU and mem speeds (with EVGA Precision X) fixed the problem. I didn't see a noticeable performance drop btw, and to me it's a better solution than all that extra fan noise.

So it's not overheating as such that's causing it (the card was only running 2 degrees cooler with the underclock) as I previously thought, more that the factory overclock isn't stable under the extreme loads this game causes.