Nah I don't think It's scheduled maintenance cause of two reasons:@frazgta! It might be scheduled maintenance slowing your system down.
OR if you could describe your issue a bit more thoroughly.
1. The CPU/ RAM/ HD usage (in task manager) are normal (0~5%) whenever the system slows down.
2. I checked the Scheduler to see if Windows Defender/ Defragmenter had any scheduled maintenace at that time. Which it didn't.
The most recent thing I'd installed was an update to a wireless driver. I've uninstalled that, but it's still happening.
Detailed Explanation:
It's like everything (browser,explorer,vlc,office) either slows down or stops responding for a while. Everything (Stats) look normal during that time.
A restart fixes it. Usually.