I can make my eyes do that too. But, I do have Congenital Nystagmus. It's annoying. my eyes go back and forth,which is beyond my control and i see slightly double, especially when watching tv. i've just learned how to use a computer about a year ago. I needed to enlarge the font to make it easier ion the eyes. That's just the way it is!
I can do this too! I've been able to do it since I was about 12, I thought I was the only one and I used to impress or (freak out) other kids in school with that trick!
As long as you don't "make" yourself do this, it appears that you won't have the symptom. Of course if they always do this on their own then that is certainly reason for concern. Please see an ophthalmologist for a comlete eye examination to check on the overall health of the eyes. If everything turns out totally normal, it could be that you can just do something funny with your eyes fand make them have "pseudo-nystagmus" for lack of a better description.
Michael Kutryb, MD