IMO, "nodding" is a twilight state, where you are almost asleep & having these weird vivid dreams. Basically your mind is seperated from your body & you are in an apathetic state of absolute peace.
For me the best nods i've had are when i'm awake one moment then the next i'm reading a book, & its all from your memory, then suddenly you go to flip it to the next page & suddenly you jolt "awake" to find there's not even a book in your hand!
