The first time I learned there was a name for this was when I mentioned it to my brother and he said he heard about it it on NPR, that other people had experienced it, and it wasn't associated with a slow descent into dementia.
But it is still terrifying even if you can name it. My last 'episode' was yesterday when I tried to take a nap. This time was different as it involved the 'intruder'/incubus phenomenon - I awoke to see something entering my apartment and move past me, and I couldn't react or move at all. I knew it was another 'ISP'/sleep paralysis event and stayed calm, then started counting which led me to believe the whole thing lasted about 30 seconds.
I could still move my eyelids and eyes, and tried twice to go back to sleep but each time I was reawakened by a dreadful feeling that sleeping might actually be a more permanent condition, so I forced myself to stay awake and try to take in the experience.
Why did I post this? Because it is helpful to know you're not alone.
To be nobody but yourself in a world which is doing its best, night and day, to make you everybody else means to fight the hardest battle which any human being can fight; and never stop fighting.
e. e. cummings