Thank you for updating me with that information. While you're in Task Manager, sort the Processes tab by CPU or Disk usage and see if any process is consistently active. If you notice anything, please tell me its name or take a screenshot of the process tab window and post it in your next reply.
You may also try to boot and test in Safe Mode.
If the issue doesn't occur in Safe Mode, that would suggest a third-party application or service is likely causing the behavior.
https://support.microsoft.com/en-us/windows/experience/startup-boot/windows-startup-settings