Since there is more than one possible cause, there is more than one possible solution.
Try the suggestion to just let it run for a while. Windows might be installing updates.
If it's a desktop, turn it off, open it, and blow it out with canned air. If it is a laptop, make sure the exit vent is blowing out air. Turn the laptop off, and shoot a short blast into the exit vent.
Install the free Wind Patrol program. It has tabs to let you see your start-up programs. Don't disable anything that says "Microsoft," but you can carefully disable one program at a time to see what happens.
Go to Task Manager--File--Run New Task. Type powershell into the box that appears and check the box giving you Administrator Privileges, and then hit Enter. Give PowerShell several seconds to load, and type sfc /scannow into the command line. It will take about an hour or so to scan your hard drive for corrupt files. (I don't think that's your problem, but it won't hurt).