Hello folks,
just wanted to share my experience. I'm no expert, but surely not a rookie either; said that: I searched the web tirelessly for solution with this issue. I have a brand new Asus ROG Laptop and couldn't understand why with all it's processing power (after a couple of months of usage) it would get kind of stuck on startup (Win opening fast, but then you had to wait several minutes to be able to open say chrome and use it, it would simply load forever). Found out that Defender was using more than 2gb of memory during these "episodes" so my search began... I'll make this short: after all the things I checked, it was freaking Itunes.... can't really say how or why, I had a hunch and it paid off; uninstalled Itunes, now starts like a Ferrari! :D
If you have the same issue, I'd probably investigate your last installed program (this was not my case, but you have to start somewhere) or tey to check programs like "MyAsus", "ArmoryCrate" and "Gamefirst" and see what program they're buffing for no reason.
Hope this help someone.
Ciao ciao ;)