So after a reboot, it works fine for awhile? If so, Safe Mode probably won't help but worth a try.
I agree to scan for malware. It seems odd it works fine in open windows of 3rd party apps and only lags on the desktop. Pretty much all the other complaints I found report lagging everywhere, or only in apps but not the desktop. Yours is only the desktop. ???
If you drill down into a drive with File Explorer, does it work fine then?
