I can't seem to find any explanation of why I get these hallucinatory(?) effects from time to time.

http://www.medhelp.org/posts/Anxiety/My-brains-has-these-fast-motion-periods-where-everything-around-me-is-going-in-fast-motion-what-is-it/show/694274

This link describes pretty well what I feel, yet I have been to several sites where people are asking similar questions, but no-one seems to be able to give an explanation of what it is or why it is happening.

I am 27, but I have been getting these experiences about once every few months since I was about 8 or 9.

I am relatively healthy (180 cm, 82Kg), play sport pretty frequently. Nothing in particular seems to trigger this, except it is usually when it is quiet when it happens for me.

No history of mental illness in my family. No prior mental issues for me personally either.