PC occasionally won't boot until PSU is reset, MC unable to diagnose problem (video attached)
Basically all I have to say is what's in the title. Brought it into MC, they thought it was my cable extensions and well...those are gone and the problem is still there. I really can't figure out what's going on with this darn thing 
Here's a video (1 min) showing the issue:
https://drive.google.com/file/d/1k3Tk2c6ONNtCoNUTi8l-ShPgVzdZt6Kk/view?usp=sharing

Here's a video (1 min) showing the issue:
https://drive.google.com/file/d/1k3Tk2c6ONNtCoNUTi8l-ShPgVzdZt6Kk/view?usp=sharing

Comments
I do apologize you are having issues with the computer. based on the issue you are having i would have to believe this maybe an issue with the power supply itself and that the motherboard itself is detecting an issue with the power coming in and preventing the system from turning on. When you turn the power supply off and back in it discharges the the power that was in it and reset the psu and then allow it to boot at that moment. do you have another power supply to test in the computer?
We appreciate the video and you've provided us with a lot of information. Now lets go over what we can tell from what you've shared. It sounds like it's some overcurrent protection. Now if this was triggered by the power supply, we wouldn't have standby power, so we'll assume it's the board. First thought would be it's triggered by a USB device. And I'm assuming this happens when the PC is in hibernate or shut off. They're really both S4.
Three things I would suggest trying.
1. Disconnect all USB devices the next time you either let it sleep or shut it down, see if the issue will persist.
2. Disable ErP in the BIOS. This setting provides power to USB devices when the PC is shut off. See if the issue still persists.
3. Kill S4. From an elevated command prompt or powershell type: powercfg -h off
Note: You can toggle this back on later with: powercfg -h on
Please let us know what your results are.
No, disabling S4 means when you shutdown, you'll go into S5 which is off. You can still provide standby power to USB devices in S5, so disabling ErP is still important to test alone. Please lest us know what your results are. Also, having standby power doesn't entirely rule out the power supply. This could simply be a bad unit, that fails to turn on without a discharge. Standby power just means it's not an issue with a shutdown in S4 because of an OCP trip.