They're called 'Sleep-Paralysis'. I'll try to explain it:
The following happens: I wake up, or at least I think I'm waking up. I see clearly the room
around me. Maybe it isn't the room though. Ok I'm awake, so I might as well get up. But it
doesn't work. I'm not able to make the slightest move, even sometimes I can barely breathe. In complete paralysis I'm lying here, nothing works anymore, and that's enough for fear overcomes me. Real fear. In addition to it, there are some eerie noises coming out
from the dephts of the flat or shadows flitting by out of the corner of the eye, or I just know there is someone or more and they're coming closer with evil intentions.
Though the impressions are very real, nevertheless I realize I must be dreaming, or rather
I stuck somewhere on the way to awakening. Alright then, now I really try to get awake.
Which is not that easy and costs a lot of willpower. Like being under water and have to get all my strength together for struggling to the rescuing surface. After the definite wake-up, the strong emotional impression, the fear, may cling on a few seconds. However, what remains is the feeling of having just conquered something really big.
Perhaps this sounds like complete nonsense, but such things used to happen not only to me but even to some other people I had asked about.
What happens there to me or to others is the so-called 'Sleep-Paralysis'.
More of it: everyone gets during sleep in this state, namely in the phase of dreaming.
The paralysis is supposed to prevent the movements we're making during a dream, so we can't hurt ourselves or the one who lies beside us.
During the awakening it's coming to synchronisation-problems. The impression to stuck somewhere between to be awake and to be dreaming in fact isn't that wrong. While the conciousness itself is moving towards awake, yet the body is not nearly as ready and still stays properly tied-down.
I'm wondering if you people ever have had similar experiences as I had. It would be
interesting to know B)

In that case - goodnight.