jesse is right... my guess is that you have some emotional/mental ties that your "subconscious" or something is trying to bring out and deal with... follow jesse's advice and face what is there... don't label, judge, or expect anything... just observe and let it play out. if you are flopping around the room uncontrollably just observe what it feels like.. notice the feelings that arise... just allow what is to be.

let us know how it goes...

dont worry about fearful things like dying or never "waking-up" from your experience... you will be fine... in fact you will be better off after facing this phenomena.