When you power up does your Computer HDD LED light is on or flickering before your reboot again?
This would indicate that the Windows Drive is running and booting up.
If it is that indicates that your computer is booting up but without any video, at least during POST.
I would wait until the HDD LED stops flickering or turns off for at 5 minutes before rebooting.
I had a similar situation when I upgraded to a Ryzen Motherboard. I had no video output during POST and Motherboard VGA LED light was on.
But once it left on because I noticed that the HDD LED was flickering or on and when it started to boot into Windows I had video output.
But when I connected my HDMI 2k TV set I had video Output during POST. It was my 4k Monitor that was causing the issue.
But if your HDD LED light is turned off after powering on and stays off then it means that Motherboard is not booting up at all.
What Trouble LED are lit when you power on the computer? CPU, VIDEO, BOOT, or RAM LEDs?