Are you holding the power button at some point by any chance? See power button menu in page 66.
Did you try changing the option “After Power Failure” in BIOS?
These machines are mounted on the wall, so I don't think the power button is ever being pressed on startup.
After Power Failure is set to "Power On".
"Wake System from S5" is selected.
"Wake on LAN from S4/S5" is selected, but we probably do not need this option.
"USB S5 Power" is deselected.
"Wakeup Hour" is set to 4. The other "Wakeup *" options are set to 0.