Firefox is grinding my HDD for no reason and lagging
If I've been leaving Firefox (v83.0, 64-bit) open for a long time, it's because I'm on Facebook and YouTube. However, after long sessions on Facebook, when I switch to YouTube, I'll get two really annoying effects:
1) When I start watching a video, the Firefox browser will start grinding away at my hard drive, as if Windows Defrag function started running in the background - that level of grinding. I know this because I checked it with Windows Process Explorer, and there were multiple instances of Firefox running, sometimes as many as 7 instances. I don't know what Firefox is doing, but it was impacting my computer's performance, **even if I stopped the video I was watching and all other programs **. The only way to get it to stop was to close Firefox, and then re-open it with Restart Previous Session, and then it quit.
I don't know why Firefox needs 7 sessions open at once, but they're not mine, and they're grinding performance badly. Can anyone tell me why this is happening, and if it's possible to stop it?
2) Linked to #1 is a huge lag problem at times when I use YouTube, which goes away when I restart Firefox. I'll click on a link in YouTube, and literally nothing happens for as much as 3 seconds. Restart Firefox, and it goes away.
I'm wondering if there's a huge memory leak in Firefox, and if there's any way to check that.
I've got 32 GB of RAM, an I7 CPU, and hundreds of GB of disk space, so none of this should be happening. Any ideas?