Some years ago (maybe 7 or 8 - I seem to remember being single) I'd often have some weird experiences in my sleep.
I would wake up in the middle of the night and be completely paralyzed. Hearing, feeling and thinking as if awake. Not seeing, naturally, since I couldn't force open my eyes.
It happened maybe once a month over a period of 4-5 months. At first it was quite scary. Once the sense of capture seeped through my sleepiness, a huge sense of claustrophobia would kick in. I would start struggling, trying desperately to move a limb - sit up, flail an arm, get those eyelids up. Sometimes it resulted in a violent break-through. I must have looked like an unlucky fish out of water, caught up in my sheets, gasping.
Later on, I actually got used to it. Tried to go with flow and sense the physical state I was in. It was virtually impossible to go back to sleep, though. The feeling of powerlessness was usually too heavy to ignore.
It concerned me a great deal, of course. I also had a lot of "falling into sleep" in the literal sense of the expression - most people have probably tried this. The big sleep-dive that has you jerking like an idiot.
I researched it and became aware of the medical concept of "sleep paralysis" (although the phrase had not been so accurately coined back then). The human brain sends signals - in the form of hormones and neurotransmitters - to the muscles, telling them to ignore physical instructions during the dream sleep phases. Sometimes the brains sends too much or lets one wake up before the effect has worn off...and then you're in the iron maiden.
It hasn't happened to me in a long time now. Probably because I never get as much sleep nowadays as back in my student days. Fuck all risk of me waking up late at night these days =)
This fun article / tutorial spurred my memory, however. I have had lucid dreams, too - but I only recall them dimly, none of them so totally in control as the article suggests.
I'm not sure I want to experiment with my dream phases - but it is tempting. The absence of logical coherence when you're dreaming is fascinating, especially because that same absence seems so perfectly natural in situ.