My desktop computer experiences random long delays where all windows freeze for 20-30 seconds or so, then goes back to normal. Happens once or twice a day. Sometimes the mouse freezes, too. Sometimes it doesn't. I know the F: drive has to spin up after it's idle, but that's pretty predictable. This is different. I have SysInternals' process explorer running in the system tray, and it's not showing any CPU-bound process or anything. The logs don't tell me anything either.
How do I even start to troubleshoot an issue like this?
My computer is several years old, and was a Windows 10 upgrade from Win7. It's been through at least a few hardware changes along the way. For instance, I had a mirrored disk and one of the mirrors conked out (and I've taken it off line).
To be clear, I'm seeking an effective view into what's going on at those key moments. Or a fix. Or a clear explanation as to why it can't be fixed, with references.