Strange waking dream-like sequence

[KRDecade]

This has only happened to a few times, so far, but it freaks me out every time.

When I go to bed, it usually takes me a while to go to sleep, so I do my fair share of tossing and turning. Lately, I've tried to go to sleep right away, and this is what's happened:

I'll start to remember something, while I'm still pretty awake, and I'll recall a memory of something that happened to me. Except, after about a minute, I'll realize that something isn't right with the memory, and I'll realize that I had no part in it at all - that it wasn't my memory to begin with. And then I'll forget about it completely. Kind of like a mini-dream or something.

I'll sit up in my bed and even try to remember the memory out loud, but it's only a complete blank.

This wouldn't bother me if I had fallen asleep and then woken up immediately after, because I would at least know that it was a dream. But this happens while I'm still (at least) half awake. And it is really freaking me out. I can't remember (at all) something that I thought of a minute before. 

Has this ever happened to anyone else?

[Xanth]

It could be a repressed memory.
It could even be a past life memory.

It could be something you've completely made up for your mind to entertain yourself.

Who knows. 

[Timandra]

KRDecade, I have had exactly the same, several times. What I noticed with myself is that I don't have to be that relaxed or in trance to be able to get the hypnagogic imagery. So I think it is just that, hypnagogics. The fact that the memory completely disappears is annoying to me and I don't understand it either, but it doesn't freak me out.