I may experience the same thing (or similar), at times I wake up with some new insight or idea repeatedly cycling through my head as though my conscious mind is desperate to remember...almost as if from a gift from my subconscious...or from somewhere in the deep dark places of sleep. It's usually a song like a piano composition, a work of art, or an interesting saying or observation. It's like inspiration direct from...somewhere. For me it usually happens closer to waking in the early morning hours, but is definitely non-REM, or at least non-dreaming. We talking about the same thing ya think?