My first exepriences with this was when I was around 12 years and I was usually sleeping on my side. I would struggle to regain the control of my limbs, but for some reason I was never scared, and fortunately I never had hallucinations. I do not know about niacin, but sleep position has no relation to my experiences.Giambattista said:
For a while I had paralysis very often, and occasionally I slipped into paralysis immediately after I had regained control, and it has also happened that I only regained control over some parts of my body but not others (like, I could open my eyes, but still not move the limbs, or I could move my hand but not the arm).
Eventually I also found out that it was not important to get out of the paralysis state, so I learned just to fall to sleep, and paralysis stopped being a problem. I am now almost 50, and I experience it less than once in a year.
I have had light hallucinations, like a feeling of floating above the bed, but that had no connection to paralysis.
Lucid dreaming is very common with me. Though I can be aware that I am in a dream, I can be frustrated that I find it ridiculous, or that I still cannot decide the direction of the dream. Usually, I just let the dream "happen", safe in the knowledge that it is only a dream. But again, I see no connection with this and sleep paralysis.