Since upgrading my XPS 8700 from Windows 8.1 to 8.1 Pro (via the Win 8.1 Pro Pack upgrade) every time I shut down the system - no matter if I use the "charms" power button or the shut down option from the half-baked "start button" - my computer restarts. I've checked Microsoft's Windows user forums and followed one suggestion to turn off fast startup, but this did not solve the problem. My computer would occasionally restart rather than shut down when running Windows 8 (the original OS) and 8.1, but now it happens every time I shut down.
ODD ASIDE: My two year old Inspiron 620, which supposedly wasn't upgradeable to Windows 8 from Win 7 shuts down running Win 8.1 Pro with no problem whatsoever.