When I shut down (even Shift + shutdown or hibernate) the computer (i5-4460 with 16 GB Ram, ASUS H97m PLUS) the PC instantly reboots. Have to do hard shutdown with power button.
I have tried a few "fixes", e.g.
In Startup and recovery, used "Restart" for clean start,
Start in "Safe Mode",
Untick "Automatic restart",
Removed or substituted all devices, hard drives plus mouse and keyboard, even monitor and RAM, except Graphics card - no fix. Defragged and scanned hard drives for errors.
Pressed power button with power disconnected.
Re-installed Windows and updated.
All fans and heatsinks not clogged with dust.
Edited Registry = "No Auto Reboot With Logged On User"!

I have recent system images saved but none before the problem started!

Any suggestions? Thank you, David