Keberoxu
"I try to get on my feet, and although I can move my torso and arms, I can't get my legs under me, and I can't pull up my core abdominal muscles enough to get above my legs"

That sounds as if your subconscious is remembering what it was like to be about six months old. I used to have similar dreams where I tried to run but my legs wouldn't keep up with my body and I staggered or fell over, as if I was about eighteen months old.