I have an i3-8109U and realise that it has not been setup to restart after power cut. I therefore restart hit F2 and get a number of options including the bottom one - Setup (or something similar) I select that and the screen goes blank.
Any help appreciated.
1. "I select that and the screen goes blank." If you only selected this option, but didn't save dose settings (i.e. clicked on F10 confirmed by "Y" or in other way confirmed saving the new settings), noting should be change. If changed, you did something more than select a new option in BIOS.
2. What is your NUC model? i3-8109U is a CPU type rather than NUC model. Do you have NUC8i3BEx?