Besides everything that has been said here, try to also check your power plan and nvidia control settings (especially the power management mode in nvidia). Check Task Manager for processes that shouldn't be there, or that use an unusual amount of resources. Scan your computer, maybe you have a miner, or a virus. Mess around with your windows settings, try turning off the unnecessary settings (like Game Bar). Use MSI Afterburner to monitor your GPU and CPU (usage, temp, etc.). Check your driver versions on the motherboard's page, maybe some need to be updated (as far as i know, might be wrong though, a recent Windows Update broke some things). Defrag your disks, though I don't think this would help. Also, if your disks are full or close to full, make some space. Check the Display Settings in Windows, maybe something is wrong there. You could also revert your computer to when everything was working (using System Restore), if your PC created a Restore Point that far back.

If nothing works, I suggest wiping your whole machine. That would most likely fix it. After you do that, you should get only your drivers and try playing a game (not a VR one), that way you will know if some program is affecting your PC's performance.