I like to differentiate that state from "sleep paralysis" for a reason I'll explain later.
Anyway, from time to time I could actually get past this state and perform an astral projection. I never managed to choose where I was going to even though I tried - I read some people could, but I was just left disappointed. However, some of the places I went to were very cool.
My first astral projection was in the car, and I thought I was gonna die. I was just sitting idly, a bit sleepy, when suddenly I was fully aware and couldn't move myself.
Regardless, there was always a presence. A... positive presence, but I felt like the reason such a positive presence was there (even if just in my mind) was because I needed to be protected, which scared me.
When I was around 15, these projections happened more and more often... everywhere, with more and more the feeling something evil was around. One time it happened in the class room, and I astral projected to some place completely dark, with voices around me saying stuff that while I was understanding, I was also aware that I wouldn't remember... and I don't. Depending on your state of mind you simply don't remember the details of an astral projection, and even when you do they start fading as the days goes by unless you write it off somewhere as soon as possible.
Around that time my grandma died. Some days after she died I astral projected and felt attracted to the bathroom. I saw in the bathroom then a human decomposing, like a zombie, staring at me, although it had no eyes. It was /easily/ the *scariest fucking shit* I ever saw in my whole life. I tried to scream but I couldn't, but my shock was so huge that I heard the scream in my head, and woke up because of the shock.
My projections were never crystal-clear, but were clear enough to provoke reactions in me. Imagine walking to your bathroom and seeing a ghost zombie staring at you. Not a movie, not a dream. It wasn't real either, but it was the closest it could ever get without being a prank.
I was starting to get really scared with all these events. Then one day, the astral projections stopped.
They ceased. Even when I tried, I couldn't do it. There was some event that happened back then... but I can't remember. I probably do remember the event itself if I had to review my whole life, but cannot link both anymore, if that makes any sense for you guys.
I had a leftover though. Sleep Paralysis. I still have Sleep Paralysis up to this day... and it happens often, but not much. However, it's clearly different - there is no spiritual feeling or anything about it, and I can't control any high-pitched vibration sound.
However, I hear very loud screams, and see phantasmagoric images on my head. Wikipedia sucks as a reference but they call it hypnagogic hallucinations which "Some scientists have proposed this condition as a theory for alien abductions and ghostly encounters". That makes complete sense... in my case, I have these images of demons and ghosts screaming. They're not very real when compared to the astral projections I had (which is an entire new level of perception), but good lord, they're fucking scary
After all those years though I became - surprisingly - an incredible disbeliever of any huge spiritual realm or entity. I was so overwhelmed by all those situations that they /had/ to have an explanation. As I started to read about astral projection as a brain state, I found some relief, I guess. From there I tried to build my own explanations for everything else, trying to minimize the odds of going crazy with that. I guess, seeing spirits all the time is not a condition humans are supposed to be in.