Graphical Performance issue

Hi
Recently I updated the game over Steam to an affliction patch, the game runs normally on start, but after 10 seconds to 15 seconds, the screen becomes increasingly pixelated. it's like a steady decrease in resolution quality from 1440*900 to 800*600 over 15 seconds. however, if I switch to the skill tree section, the resolution becomes normal again but it starts over again. my GPU is Asus 3060ti. I also update my GPU but the issue persists.
Thanks for helping me in advance.