Hi,
It's not just a problem that one person or one machine is facing. We have 4 NUCs that are all experiencing the same problem intermittently. Sometimes they'll boot without a monitor and sometimes they won't. It's totally random for us and very frustrating as we'll boot them remotely sometimes and then they don't come back up without connecting a monitor.
Also, as mentioned above, it doesn't even get to the stage of loading the operating system, so it looks to be independent of the OS. We're running Ubuntu on ours.
Regards.