Question Boot problem after replacing the video card

[Ab23]

After replacing the video card, the computer wouldn't boot and the monitor screen was black (there was some signal but no image), I couldn't even get into the bios.
I tried many recommended things for such cases as removing various components, clearing CMOS, etc. and the only thing that helped was turning the computer off and on many times, when suddenly for no obvious reason everything started working properly.
The computer then run with no issues for several weeks including demanding games, until I took out the video card and put it back (there was some fan rattling I needed to check), the problem repeated and resolved in the similar way as before.
What could be the cause of this? I'm afraid to touch the hardware anymore now that I'm not sure if the PC will boot properly.

My specs: ASUS PRIME B560M-A, Intel Core i5-10400F, NVIDIA 3060TI (connected to Dell monitor and Philips 4KTV), 16GB RAM, 1x NVMe SSD, 2x SATA HDD, Silentium Elementum E2 550W 80Plus PSU.
Max power draw during booting is 110W, idle in Windows is 60W and 240W in the most demanding games I play. I used PSU calculator on the web and got recommended PSU Wattage for this system 440W.

 

[Ab23]

I searched the net a bit and try to reply myself. I suspect it may be some electricity issue. My PSU has a physical switch that I used when changing the card. But I found this on Quora:

"The usual recommendation (when changing the graphic card) is to leave the computer plugged in but the power supply switched off with a physical switch. The downside of this is that the power supply will still produce standby power, so some things on the motherboard may be energized.
If you have a power strip that you can turn off, that’s the best approach. Plug the computer into it, plug the strip into the wall, and 100% confirm that the strip is off. That will keep the ground connected but not allow any power to get to the computer.
You can also just unplug it and use caution. Don’t move around more than necessary while performing the swap and, if possible, touch something grounded before doing the swap.
If you want to be fancy, get a grounding strap, but it’s not necessary. Whatever you do, do not ever connect a person directly to ground. Grounding straps have a large resistor built into them for safety."

So maybe the power isn't completely turned off with the switch (only some PSUs do this), or maybe some charge remains long after the power is turned off.
I won't experiment with it now, I'm glad the computer works. But the next time I replace the card I'll try to use a socket that can be turned off or try to discharge capacitors by holding down the case power button with unplugged PC.