OHHHH....
That's the power saving on the monitor... It's a known issue on samsung monitors and some others with the new eco modes, if the monitor goes into a long sleep (deep sleep) it will not start up with the pc and shows a error on the motherboard with dp stating VGA error.
Turn off all the eco rubbish in the monitor settings there is more than one place to do it.
An easy test for it is shut down the pc let the montor turn off first and then turn on the pc right away (within 3 or so mins) and it will start up on dp and show the bios and windows loading. If the monitor has been off a long time or it went into sleep mode in windows for a long time same thing will happen.
You can easily test it this way too if the monitor has been off a long time and pc is shut down, turn on monitor first with the power switch and then turn on the pc, again it will work right.
See same issue here :-
https://forums.overclockers.co.uk/threads/samsung-monitor-doesnt-automatically-turn-on.18937543/
I only know that because I got hit by it too, with the samsung CRG G9 when I got a 3090.