Sudden stutter/FPS drops until reboot

Started happening in this league:

At a random point - sometimes after 5 minutes of gameplay, other times after 4 - the framerate will consistently drop from 70-90 fps to 10. no settings changes will work except rebooting. there are also random "jags" and stuttering that will start to appear after half an hour of gameplay or so - drops to 1 fps that freezes the game for a couple of miliseconds. A reboot helps, but now I have to reboot after every 30 minutes...

Vulkan, settings low (still same problem), RTX 2060 Super, dual xeon E5-2689 with 100gb ram.