So you wake your Windows 10 computer from sleep (or hibernation), and the fans start humming. You see that the System process is using all of one core, in one of the threads with root address SeAccessCheckWithHint+0x1c620 . It runs for a good half hour, then stops. What's happening?

Probably the issue is a scheduled memory test, which *should* pause when you use the system, but which often doesn't. You can see whether this is your issue by opening Task Scheduler, then selecting Task Scheduler Library/Microsoft/Windows/Memory Diagnostic. If RunFullMemoryDiagnostic in the top pane says Running, then this is your problem. You can stop it (for now) by selecting End from the context menu. You can make it less likely to interrupt you by selecting Properties from the context menu, then setting Conditions/Start the task only if the computer is idle for to the largest-available setting (1 hour on my system) and Wait for idle for to a small number, say 1 minute.

Kudos to "chasm" at for discovering this solution, and persisting in posting it even after being incorrectly downvoted.