Wow I can do that too, sounds exactly the same! I've always wondered what I was doing. SNS sounds about right. I always wondered if it might be changing my skin conductivity too, it feels kind of buzzy. I'm pretty sure its not just in the mind.
When I was a kid I started getting alice in wonderland syndrome which is harmless fun if you ask me. I learned to induce it, kind of meditating, and discovered other weird things like this buzzy feeling. Something else odd would happen sometimes like my head would feel like it was vibrating back and forth at about 2 Hz.
I guess 4 billion years of evolution has left a few bugs lying around
