I had this issue and it turned out my Clubsport pedals were causing a USB conflict with MSFS2020, but only if I installed my pedals ‘after’ installing MSFS2020. So if you have installed a USB device after MSFS2020 was installed it could be causing a conflict.
Obviously the easy way to check if any USB devices are causing a conflict is to unplug them and run MSFS2020.
Although in your case it is more likely your GFX card, if its not up to the job