My symptoms were identical. I'd restart the explorer process, CPU would go to normal, but then remain spiked once I open an explorer window again.
I observed that once I opened the file explorer, 'quick access' in the URL bar would display a progress bar, as if a search was running.
bobpettit from an earlier post mentioned his fix was deleting a corrupt PDF on his desktop, so I looked for any "defective" files that I might have had. What I hit upon was a MKV file I had in my downloads folder that once opened, appeared corrupted in my player (because it would play the audio but not the video).
'Quick access' will show recent items you've opened (if the feature is enabled). In my case, it was. One of the recent items was that MKV file.
I disabled the 'recent files' feature, restarted the windows explorer process, opened an explorer window back up, and the high CPU use stopped. To disable/enable that feature:
- Open Settings.
- Click on Personalization.
- Click on Start.
- Turn off the Show recently opened items in Jump Lists on Start or the taskbar and in File Explorer Quick Access toggle switch.
You can then turn the feature back on after you've restarted windows explorer, but either delete the culprit file or never open it again!