When you see the CPU run at 100% percent check Resource Monitor via Task Manager and see which apps or programs are running at the time:
It is possible that an app is running some sort of background scan like your Anti-virus program or some other app.
You can enter a Clean Windows Desktop which is the same as running Windows Safe Mode while in Windows desktop to eliminate any 3rd party app causing the problem. It basically disables all 3rd party apps and Startups and just leaves MS apps and startup enabled. Easy to do and undo: How to perform a clean boot in Windows
Enable the apps that will let you run the games and see if the issue occurs or not. If it doesn't then by the process of elimination start enabling 3rd party apps and startups and see when the issue starts occurring again.