What is this sleep/dream 'paralysis' phenomenon called?

This is not uncommon, I think it is just referred to as sleep paralysis. It happens because your brain paralyzes you when you’re asleep so that you won’t start acting out your dreams (sleepwalking is a failure of this mechanism), and sometimes, in some people, this mechanism keeps working for a bit too long after you’re awake.

Yeah, ‘sleep paralysis’ is all that it’s usually called. I’ve had it happen a few times, it can be pretty terrifying, i agree. It’s actually got a very long and rather interesting history. For instance, in the middle ages people thought it meant a demon (specifically an incubus/succubus) was trying to ‘take’ you.

Also, it can wrap up with dreams and make you see things, which can be even stranger. I once ‘woke’ and saw fingernail-eating caterpillars all over my room. Yeah, glad I got out of that phase…

Sleep paralysis from the wiki.

The others are right; you’re talking about sleep paralysis. It happens when your body is still in REM mode but you’re awake – the body is “paralyzed” in REM sleep (it’s called REM atonia). Check out the Wikipedia page on sleep paralysis – there are a few links at the bottom of the page as well.

It’s sleep paralysis, all right. And it can be accompanied by hypnagogic hallucinations, in which you are perfectly certain you are awake (unlike in dreams where you think you’re awake—the difference is very distinct) and can later report events that you truly believe happened, but they didn’t.

I’ve been troubled by occurrences of this ever since I was a teenager. It’s the most terrifying thing I have ever experienced. Sometimes months will elapse without an episode, and sometimes it will occur several times in one week. I go to considerable lengths to avoid it, feeling certain that one night my heart will burst while I struggle to break out of it.

Here’s a much more detailed answer. You will also find several other Fluther threads on this subject if you search on “sleep paralysis.”

I’ve experienced it a few times. But mine doesn’t usually work well enough and I sleepwalk all the time. That’s not as scary but tends to be a touch dangerous. If it reoccurs you might want to ask your Dr because it can be a symptom of other conditions.

May i thank you all for your informative answers and links.
It is also nice to learn that i am not totally alone in this (although i already knew that also my girlfriend experienced it a few times).
Thank you!

It is not that uncommon and is sometimes called Old Hag Syndrome

Yes, it is a dream paralysis state, happens to me once in a great while.
I am a lucid dreamer, can almost always question myself during the dream state and be aware that I am only dreaming.
Infact, this happened about 3 months ago one night. I was awake and aware that I was coming out of a bizarre dream but couldn’t move for a few seconds, maybe 20–30, but..the whole time I was saying myself ” this is only a dream.” haha

One thing I’ve tried to train myself to remember is this simple fact: “If I’m awake, I can open my eyes.” If I can’t open my eyes, then, I must be asleep, even though I think I’m not. And if I can pop my eyes open, I can also come out of the trapped state.