I just experienced it once in my life. It was spontaneous anyway.

I was lying on my bed with my eyes closed trying to sleep as I think we all here do. Suddenly, I felt like I wasn't really tired to sleep so I tried to stand up to turn the TV on, but I couldn't. Literally, I couldn't move. I didn't feel dizzy or hear something. I just can't move. I was really scared, but I calmed down and 'regained' control over my body.

I breathed a sigh and tried to sleep again, and without any transition I got paralysed. After a few minutes, I could move again to turn the TV on and after 10 minutes, finally sleep.

Honestly, it wasn't scary at all, but it freaked me out.