|Try updating graphics driver from Nvidia.|
4 Min. after boot up sounds like possibly your antivirus program downloading virus definitions and checking for updates, or another program doing daily updates (Adobe possibly) at boot up. If the driver update does not help, look into what processes are running (possibly many) at boot up and see if disabling them from starting with Windows (msconfig, start tab) or if rescheduling some them helps.
You have to be a little bit crazy to keep you from going insane.