I can't be certain because I've never had this exact problem. But it sounds like it might
be connected with the anti-aliasing settings that you're using. The graphics resolution you select for GPL only affects the 3D racing screens. When you're back in the pits, looking at the various menus, car setup screens etc, GPL always reverts back to 640x480 resolution. If you have a high anti-aliasing setting selected in your graphics card control panel, it can make the low-resolution screens look blurry. The fact that you say that the screen looks sharp for about a second suggests that you might
be using some kind of "multi-frame" full-screen anti-aliasing ("mfaa"? I'm not totally familiar with the very latest acronyms.), which averages out pixel values over several frames. This technique can take a moment to become active when you switch screens, as it's busy doing calculations on the first few frames.
Try adjusting the anti-aliasing settings in the graphics card control panel, and see if that makes any difference. If it does, then you will have to experiment to find a compromise setting which still gives good AA for racing, but which also reduces the blurry effect in the menu screens. Good luck!
Edited by Saiph, Mar 09 2019 - 06:01 PM.