Hello of1973,
Let me help you with this.
If you are having problems to enter the BIOS it could be that Fast Boot was previously enabled so here are some troubleshooting steps you can try to fix it:
- Turn the NUC completely off.
- Press the power button to turn it on but immediately press it again and hold it for 3-4 seconds.
- Turn it on again.
By doing this, you should see a screen similar than this one:
Kevin M