Weird sliding head feeling?

The other night I woke up naturally, and went to try a WILD. I believe I had gotten to sleep paralysis (I couldn't move my arms at least) when I got a very odd sensation... I was laying on my back, face towards the ceiling when it started sliding.. At first it came started going to the left, and I could somewhat resist it. It went back into place and instantly went to the right. It was overwhelming and I couldn't resist it. I snapped out of sleep paralysis and did a reality check. I wasn't dreaming so I went back to bed normally.

Has anything similar to this ever happened to anyone? Or could someone explain what was going on?

Equilibroception hallucination. Just like you can hallucinate with the common senses, you can hallucinate that you're off balance. Since you were close to a dream, it's not uncommon that you experienced this.

I've felt rocking sensations while falling asleep, but never during SP.

This happens to me too sometimes, but as I tend to sleep on my side, it feels like the whole bed is sliding downhill! I usually startle myself completely awake when it happens -_- I'm glad you asked this question, because now I know why it happens! :)

Yeah, I think I've had this happen a few times. Never when I'm trying to go into SP or anything like that though. I get the feeling that I'm going to slide off the bed and totally bolt up. Startles me right out of trying to get to sleep :/