A normal shut down does not remove all power.  there can still be some 3.3 v to cmos
check to see if bios did not get reset on a power plug pull out (low battery or other problem )
 
I never use any fast boot or sleep mode setting and have a full re-load  restart set
 
Early SSD did have some type of  problem with no power but not ( I think)  that  one you have.
you can always check the SMART data for power loss.

I think I am explaining it wrong. The issue is that when ever the system looses AC power the following POST is delayed because the unit will turn off and back on. 
 
Here's a video of me replicating the issue. 
 
https://www.youtube.com/watch?v=0kPLjIkoTY8

Yeah attempts to post then stops turns off then post just fine and boots into Windows. This only happens if i turn off the PSU or unplug the PSU when the computer is turned off. I think its fine just something I noticed when I moved my computer back to my Office after the install of the M.2 and Windows was completed. I will have to check the fast boot settings when I get a chance. And now that I think about it. It doesn't really stay on POST CODE C its just the last code it cycles to before restarting. And I was waiting for the lights on the mobo to go off before turning it back on. 

Normal for the double power button push from a full power disconnect
Also - I am running my X299 Dark with the EIST enabled (Euro power setting) in Advanced / CPU Config to power down all the board lights and connected USB devices (shuts down keyboard LEDs) and it acts the same way on boot up

@zaphrodbox Make sure all your Cables a locked in and that all the Pins are all the way in each connector.

GGTV-Jon
Afar far as the the momentary power up / power down when turning on the PSU I have seen that on a lot of stuff, never thought it was abnormal. As long as it boots up fine on start up.
 
@zaphrobox take a good look at the connections where the power and reset buttons connect to the motherboard and make sure you have them on there correctly

This might be a stupid question but what if I unplug all of the front button connections? Would the mobo still post C say like I was running it in a test bench? I have attached and reattached every wire so many times and finally decided to just unplug all the front panel connections after re-seating all power connections again and the board still will not shut down just goes to post code C and all fans to 100%.  
It is also a ton of work to do this as if you check out my mod rig it is all behind a custom distro plate and hanging on my wall so takes a lot to disassemble and reassemble it to try and fix this issue.  The PC runs great under all other circumstances.  I appreciate the advice, but this one has me stumped still... Z390 DARK to the rescue!

GGTV-Jon
Just looked at your build in mods rigs - WICKED build there man
 
Yes, with everything pulled off for the front panel it should have worked like it did on the test bench
 
Let me get this straight now - when you are in windows and you tell it to shut down it blanks the screen like it shuts down with the post codes displaying C and the fans on high?

Thanks.
Yeah I tell windows to shut down and it will cycle some codes then end seemingly shut down but displaying post code C and all fans will spin up to 100%.  If I shut down the PSU it obviously shuts down the rest of the way, but when I turn back on the PSU it will immediately show POST C and 100% fans until I press the power button on the mobo then it will cycle and boot into windows like normal.  Very strange and does this with multiple different PSUs different wires.  I have re-seated the CPU checked pins and pretty much everything I can think of to no avail.  See my original thread about the issue but not sure there is any info not repeated here at this point...
https://forums.evga.com/Post-Code-C-m2881972.aspx