Hello, I'm having the same issue, This problem is due to some bugs with DX11. I recommend OpenGL mode as a temporary solution to this problem.
To do so, head to your Steam library, click Play on ETS2 and a small grey window will open. Choose "Launch with OpenGL" and start the Game all the way, a few minutes drive and quit. If you are not satisfied with OpenGL, change the options as DX11.