XPS 8700 suddenly slow rebooting and starting

My previously speedy Dell 8700 with 12GB ram has suddenly slowed to a crawl when rebooting or starting up. The problem occurs before any hard drive activity starts.  So, when I reboot, after the shutdown procedure occurs, the monitor goes into sleep mode (amber), the white light on the tower's power button remains on. The computer is then silent for about five minutes before the monitor comes alive, the disk activity light comes on, and the startup procedure occurs.  From that point, the startup is speedy.

If I completely power down, when I boot up, the power light turns white, the screen displays a Dell logo in a circle.  There is no caterpillar going in a circle for approximately five minutes. There is no disk activity.  Suddenly, after sitting there, the caterpillar appears, and the computer boots up speedily from that point.  Basically, the Dell logo without caterpillar is taking several minutes when it used to take a couple of seconds.  If I hit F12, it won't beep until after that five minutes is over.  So, the problem is very early on in the boot process, I would guess.

I have shut down the computer, pulled out the plug.  Removed all USB cords.  Held the power button down for thirty seconds, then re-inserted all cords, and powered back up. That did not seem to solve the issue. 

I have BIOS A03 that came installed on this machine which was purchased almost exactly one month ago. I haven't attempted to update the BIOS in fear that I might make things worse since the computer was fast a week or so ago.

The online diagnostics refuses to run. Have not knowingly changed anything in BIOS settings. Have not run diagnostics from F12, but will do so.  Cannot see how to turn on verbose POST.