Intermittent Posting Problem

[ModularOtter]

Full specs are as detailed on this pcpartpicker page.
 

My build will post once. Then the next time it starts up- the fans are humming along normally, but no video, no post. Going through the usual stuff on the "How to deal with a no POST..." thread I found that unplugging the cmos and giving it a few minutes did the trick and it once again posts... until the next power on, or sometimes I can get 2 out of it. Worse still, the cmos trick works 3 or 4 times and then it doesn't. A slightly different failure state occurs where all the fans are now blasting full tilt, still no video, no post, and now after about 10 seconds it powers itself off and back on, repeat every ~10 seconds. Once it reached this point I couldn't get the cmos trick to work again, so I took everything out and started test benching. Long story short, once on the test bench it posted immediately, so I threw everything back in, only for all of the above to happen all over again.

If I can get it to post again I'll try reflashing the bios, and I'm going to order a new cmos to see if that does the trick.
But in the meantime, do you folks have any suggestions or experience with this problem? Anything helps, thanks.