This is typical of how a spontaneous out-of-body experience begins. Once you dismiss the fear and roll with what is happening, you may find yourself in an interesting situation; try to stay calm and lucid.

I've dealt with this a bit in my practice -- I've had a handful of possible cessation events off-cushion at various times, but way way more strange abrupt transitions, loud audible static, rainbowy visuals/synaesthesia, fifth jhana onset tunneling/falling  through space, and unknowing moments while I'm falling asleep or sleeping.  It's kind of frustrating that most of it doesn't lend itself well to dharma diagnosis of cessations or path moments, although you can start recognizing your personal manifestations of the A&P with reasonable confidence.  The good news is that formal dharma diagnosis is unrelated to your ability to integrate insight into your life -- these kinds of shifts while sleeping can start shifting your baseline perspective during the day.


You don't necessarily need to do anything to special -- new unusual events or states are most disorienting or scary when they first arise.  Eventually you get more used to them and they don't seem as either disorienting or special.  You also don't need to have an intention to stay with them any longer than you naturally would.  If you're aware that you're dreaming, you can just remember that this is an unusual meditation-related experience that's showing up while you're dreaming, and that you're still safe in your bed like normal.  Don't force your mind to go into the fear more than it wants to because you think you'll get a meditation goodie from doing so, and if your mind doesn't want to go out of the fear then try to go along for the ride and remember the context.  If you're aware of your body, you can try to notice what your legs and feet feel like.  If you're in a dream state with other people, then try to remember the metta phrases and wish them well.

Thanks much for the feedback, very helpful.