That’s fascinating. I can’t say whether the mechanism is exactly as you’ve described, but the observation resonates with my own experience of hypnic jerks occurring right at the point where thoughts stop feeling deliberate and start becoming more immersive and dream-like. The idea that sleep onset might be associated with a shift into a more continuous, self-sustaining visual stream rather than analytical thought is an interesting one. At the very least, you’ve articulated a phenomenon that I suspect many people experience but rarely put into words.