How do I know if something is downloading/installing in the background (Windows PC)?

I often notice my PC becoming extremely slow (mouse movement is very slow, jerky, among other things), and websites load very slowly. All applications are closed (except Google Chrome and Epic Games Launcher). In Chrome, I can't see any files being downloaded.

I've noticed this happens when, for example, Windows Update is running in the background. Or when Epic Games (auto-download updates) is running.

But my PC suddenly becoming extremely slow is happening more and more often, and I can rule out these two things by checking to see if anything is being downloaded and installed.

I don't see any suspicious processes in the task manager.

Where can I see what's happening in the background? Whether something is being downloaded and/or (secretly) installed?