I wanted to chime in here in case others have the slow startup issue as well. I watched my console window, and the only thing that happened during my slow load was that the userprefs.blend loading message sat on the screen for a long time. up to ten minutes. Then blender would finally load. The problem started a couple of days ago for me. It also happened if I did Command line rendering. The userprefs.blend file would take forever, then suddenly everything would work again.
I found this thread while looking for solutions. I have no SD card readers, and I had no network drives connected. However, I had a blank DVD in my DVD drive, because I was working on another project, and forgot I left it in there. So I ejected the DVD.
Weirdest thing, but after ejecting the disc (with blender closed,) All of windows locked up, and would not respond anymore. I had to do a hard reboot. I should mention that when this problem started yesterday, I rebooted then as well, but it did not solve the issue. Blender remained slow until after removing the blank DVD.
But after removing the DVD and rebooting, blender loaded immediately, and my command line render worked again. as AeroLynx suggested, there appears to be some kind of file access error when certain types of removable drives are connected and Blender is running, to the point it can cause Windows to lock up.
So, if you are having issues, Disconnect removable drives temporarily, make sure all network drives are disconnected or properly connected (no red ‘x’ on the network drive!) and make sure nothing is in the CD/DVD drive.