Windows 10 freezes reproducible

I have my Setup since a good year now, anything run stable(prime95 stresstest 24H).

-i5-750 @4GHz
-GA-H55M-UD2H
-ASUS GTX670 DirectCu2

But lately its occasionally freezes. The monitor just shows the latest image, the keyboard dosnt work, neither do start/restart button. I have to pull the plug to restart. That always happens after ~10mins when im playing Dark Souls 3

I didnt install any new software besides DS3 nor could i find any relevant informations in the eventlog besides the unexpected shutdowns.