We have quite a few nucs (NUC8i7HNK) and from the 6/2018 and the 10/2018. We were setting up power on failure the device does what. We enabled the device will turn on after a power failure. WoL and a minor few.
If we unplug the device. Wait 15 or so seconds and plug it back in. The device behaves as normal.
If we unplug the device wait 2-3 seconds and plug it back in or flip the switch. The device does not power on. The power button on the front doesn't work. However if you unplug it from the back of the device and back in it will work.
We tried this on bios version 0034 and the latest. I suggested upgrading the the latest bios to a coworker who was working on this. Because I read in the release notes that it corrected the issue. Same issue across the board.
So the power button doesn't work. The bios settings are basic out of the box configuration with the exception of power on failure enabled. wake on hibernation, wake on shutdown (so s3,s4,s5)
You should update your NUC using Bios recovery method from Power Button Menu. The problem was fixed in Bios version 52. Now please update to version 54.