Hi Nick43 🙂
"there are days I wake up knowing it will be bad because of the dreaded unfulfilling yawns; even while lying in bed before getting up in the morning (ughhh it's here already)."
Yes indeed!! I know exactly this feeling. Sorry I didn't see your post earlier. Am just about to get out to plant our strawberries (!!) but would like to try and give you some thoughts on your questions above before too long.
I agree with you totally, I believe something in the study of the autonomic nervous system will give us clues to this.