High CPU Usage While Computer Locked
When I lock my Windows 10 computer, as soon as the screen turns off, the fan gets very loud due to high CPU usage. However, as soon as I unlock the computer, the CPU drops and the fan soon shuts off. When I check Task Manager immediately upon unlocking, usually the System process has the most usage (sub-10%), but I do not see any process with high CPU usage. Whatever is causing this seems to hide itself as soon as I unlock the computer. This happens even while the computer is in airplane mode. My Windows operating system has no pending updates.
I have scanned it with Bitdefender Total Security, Malwarebytes, and Spybot. None of these have resolved this problem. I heard that some malware can mine for cryptocurrency while the computer is idle. I would like to get to the root of this problem. What else should I do to troubleshoot this?