20 minutesa of Gameplay, and my system locks up. Requiring Hard Reset

About 15 to 25 minutes of play, May rig locks up entirely, with no ability to Alt-Tab or access Task Manager. I have to hit the reset button on my case. I’d really like input from a Warhorse member of staff please.

My Rig specs

Intel i7 8700k
EVGA Nvidia 770 cards x2 in SLI config
32GB Corsair DDR4 ram
1500W power supply

I’ve already tried an SLI solution (see link)

With windows Update 1809, my system randomly freezes for one - two minutes, unseen what programmes are running