I found the problem. It's my mouse, of all things. I have a Razer Deathadder that I use for gaming, and my wife gave me hers because it wasn't comfortable for her. I started having the same symptom on my 9020 MT, but only during a restart. (Cold Power on to desktop there's no issue) So I ran Dell Diagnostics on my SFF and noticed that it was having a hard time detecting the mouse and was lagging. The instant I unplugged it, the lag went away and everything went smoothly. So for some reason, DellDiag doesn't like my mouse. What I have to do every time I restart, is unplug the mouse, wait for Windows to boot, then plug the mouse back in. A bit annoying but I'll live with it.    Oh, and the random Rear Fan Failure error? I ran a quick test in DellDiag. In order to pass, it must peak at 4500 RPM +/- 10%. (4050-4950 RPM)  It finished at 4023 RPM, which is just outside of tolerance, which triggers the error.
Alright, I have this weird thing going on. In the beginning my little mighty PC would just simply boot up, and everything would work. (power on to desktop = maybe 30 seconds) Now I'm experiencing a symptom that... When I Power On, It'll go through POST just fine (I think) and I'll get a blank screen with a cursor. It'll sit there for about a minute or two. During that time, I can slowly hear the system fans increase in speed, although they don't reach full speed. HDD LED blinks, so the SSD is doing something. It will eventually boot to Windows. Once it does boot, everything's fine and I can do whatever I need. Any ideas or thoughts on this?  Thanks!
9020SFF POST/SSD issue?