[2020] Weird graphical glitch of shiny grey squares that block everything

You're most likely overloading your Vram and causing the LOD to screw up. Lower your graphical settings- Specifically Texture Quality takes a huge amount of Vram; 8gb at the highest setting, 4gb at half, 2gb at quarter.

Without knowing your exact settings and computer setup I can't offer much more info than that.