I am not a MD but is sounds like it could possibly be indicative of a sleep disorder. Possibly related to medication? Or stress? Or just an off night where your body woke up before your brain? Have you heard of "sleep paralysis?" Check it out on Google. I have experienced it several times and it is terrifying. That obviously doesn't fit your description but I mention it as an example of a disturbing thing that can happen with sleep disruption and it is nobody's fault...you emphasized that the sex was consensual. I once took a phone call which woke me out of a deep sleep and I felt like it wasn't really happening. It was bizarre. Perhaps your doc will suggest a sleep study? For now, it seems important to talk it over with your partner and emphasize that you should not be woken up for sex under and circumstances. Hope your MD helps! Good luck and best wishes