What's wrong with my monitor?

GigaByte M28U 4K 144Hz monitor

So I've noticed a lot of the time when I turn on my PC, I go past BitLocker Pre-Boot PIN screen and then my monitor switches off. My PC keeps going. If I however take out the PSU cable of the monitor and plug it back in, everything's fine again.

My PC always turns on, fans start spinning, LED lights on, the LED coloring of my PC case is also on.

To me this seems like a monitor issue. Can you help me figure out what could be causing this?

Megahertz said:

What happens if you don't take out the PSU cable of the monitor and when it enters windows you move the mouse or hit esc ?
Is fast start enable? If it is, turn it to disable. Fast start is more part of a problem than part of a solution.
Turn On or Off Fast Startup in Windows 10

Nothing, black screen

Yes I'll try doing that

Do you have a "routine" to turn on the PC and the monitor? I like turning on the monitor first and waiting until it ends its routine with end in powersaving state. My Lenovo one displays an own splash screen first. The Samsung one depends on the connector and in HDMI is doesn't end in powersaving state, so I turn on the PC when I see the small rectangle indicating HDMI. The Philips waits a bit before showing a slow sequence of two screens indicating the entry in powersaving, so to avoid it I turn on the PC first, wait 2-3 seconds (a noise done by an optical drive serves me as reference) and then turn on the monitor. Before it wants to show its "burocracy" to go to powersaving, the PC sends its motherboard splash screen.

Of course, failing with these routines or not doing them once or twice doesn't cause anything serious. This is just to try to avoid as most long-term wear as possible. And here I'm not relating your monitor's or PC possible malfunction to these "semi-rules", just suggesting that maybe there's a routine that works around your issue.

With PSU cable you mean the mains one? Is it connected directly to the mains or to other place like your computer's PSU? (I haven't seen a PSU with "monitor output" in decades, but I've never been interested in them).

Instead of detaching/attaching the power cable, have you tried other possible workarounds like powering off and on the monitor, or selecting other source and returning to your usual one?

I've never used Bitlocker myself. Could you please tell here the total sequence of screens you'd see in a normal situation? Like motherboard splash screen -> Bitlocker PIN screen -> Win10 splash screen (the one with the blue window in angle) -> "Landscape screen" (technically called block screen; there's a Win10 setting with several options for it besides what I'm calling "landscapes", that has other technical name that I cannot recall now) with PIN or login or whatever -> Windows desktop.

If I've understood it the issue is random, or does it happen always? Was this working okay till it started doing this, or it has done it since ever?

My main suspect is the computer actually, possibly fixable with a BIOS setting. It seems that it sends something wrong to the monitor.

if I shut down the computer then turn it back on. if however I press Restart instead, then there's display

What could be causing this?

Buy a new monitor

Check Device Manager for driver issues, problem devices will display with either a question mark or an exclamation mark over the affected driver. Right click on those devices and choose uninstall. Reboot, check functionality.

Go into the monitor menu and hit reset.

Try a different monitor.

Try a different monitor cable.

Does the PC have a dedicated graphics card (GPU) or does it have integrated graphics?