Old thread, but I thought I'd repost considering I just found it again while googling, and have learned more about it since then.. this infomight be useful to people..
First of all, it isn't narcolepsy. I do have ME, but that doesn't explain this (and other's with ME don't seem to experience it).
I do know one other person who goes through a similar thing, although not as strongly. He gets sleep paralysis while waking up, I get it while going to sleep.
The main link though, is that we both have incredibly vivid dreams, mine are often lucid.
Recently i've been slipping into dream during the process of getting to sleep aswell, i'll be resting in bed, and all of a sudden, i'll think i'm doing something.. in my bed usually, for example.. talking to people on my laptop..
after 30 seconds max i'll realise i'm dreaming and snap out of it.. the reason i wouldn't say i've slipped into sleep at this point, is that at the same time as dreaming, i'm aware of what's going on around me.. the two conciousness' just seem to run separately at the same time :S
Another thing that seems to be unique to me is my creativity going into overdrive before sleep, i'll conjure up new faces and places in my mind instantly with incredible detail..
As for a cause for this, I have no idea. I'm hoping that it's a result of having ME, or at least being worsened by it.. ME does affect sleep in different ways.. will have to see if it changes any as i progress through mickel therapy.
Messily written, hadn't planned it out.. but someinfo there might be helpful
Oh, on the second page of google results I found out what it is.. "Hypnagogia"
http://en.wikipedia.org/wiki/Hypnagogia
Certainly accounts for the frequency of lucid dreams I have..
And although mine are more dreamlike than what that article suggests, it is a very similar description to what someone above wrote..
I'm surprised this was so hard to find