Update your post to include full system hardware specs and OS information.
Include make and model webcam.
How many times have you rebooted your pc?
Look in Task Manager - determine if the new webcam software/drivers may have slipped in some other app or utility that is launching at startup.
Also look in Task Manager and Resource Monitor to determine if the drivers and/or software may be trying to update themselves, do some sort of backing up, or are just "phoning home.
Just a couple of immediate thoughts....
Webcam software or perhaps some other software coincidentally trying to update or backup.
Maybe some software glitch that eventually got cleared out.
Look in Reliability History and Event Viewer. Also Windows update history.