|See what is running up the CPU in Task Manager. If it is not clear, you can also use Process Explorer from Microsoft which will show you more. If the program is something you recognize, if it is not Microsoft and it is not critical, stop the process. Google anything that you are not sure about, but nearly anything that uses that much CPU that you have not launched is malware (or other nasties), or you are sharing your processing power with a university (or other project) without knowing it. After shutting down anything that is clearly driving the up your CPU usage, uninstall anything in Programs that you have never used (again Google if you are not sure what something is), rerun Malwarebytes. If you have succeeded in shutting down nearly everything, it should now find the culprit. If not, try running it again in safe mode.|
Failing these, there are others here that have more extensive tools and they can walk you through the steps to use them.
You have to be a little bit crazy to keep you from going insane.