Hi,
What games are You running?
And from which: Microsoft Windows X-box, Steam, Uplay, Origin, other?
Open Task scheduler and try to see what processes is started at the moment:
https://technet.microsoft.com/en-us/library/cc721931(v=ws.11).aspx
Check which processes and services that is most demanding, to see if something strange going on:
Start > type Resource > click Resource Monitor > open up the window so you better can see > click Overview > make sure that you can see both Processor and Disc windows.
and then sort by clicking the CPU column (in both windows) and make sure that the very tiny arrow point downwards - it will sort all the most demanding processes with the highest from top > Take a screen shot of that.
Then click the processor tab so You also can see Services, sort on the CPU column so the little arrow points.
Your system might be compromised.
Download and run free Mbam regardless if you have any other antivirus protection, but make sure in its settings not to auto-start, just run it manually every other week or so, unless you only have MS-Defender as your only antivirus protection, then use mbam at all times:
https://www.malwarebytes.com/
Best regards from Sweden