I just had a very eerie expierience. I was taking a nap, and as I was slowly drifting off, I felt my body fall asleep. I felt my muscles relax, my arms slide off my torso to my sides (I'm a side sleeper, but I like my naps on my back, else I sleep too deep and wake up all confused), and even my jaw drop as I resting my back on a big pillow and have had my body and head up high. I thought I was sleeping with my mouth open, but it was just my jaw, and my lips stayed closed together.
I wanted to try and move my arm to see if I had sleep paralysis (I was pretty excited about that as I've had sleep paralysis a couple times before in my life, and contrary to most people's expierience with it, I liked it a lot), but I didn't want to wake up in case I did manage to move it.
I stayed half aware and in controll of my thoughts for a little while, though my brain felt foggy, but my head followed soon and I just fell asleep.
It was a good nap.