This has happened to me since I was a kid and still happens every now and then if I stare at a particular object in a certain way. It's very irritating, but usually resolves itself in a few minutes (20-30) if I ignore it. I think it's a brain issue more than an eye issue - I can make it happen whenever I want.
You need to start with an exam by an Eye MD pediatric ophthalmologist. Find one near you at www.aao.org or have your pediatrician refer you.
It could be an eye condition, sometimes pediatric migraines (which may not have headache) may cause that.
JCH MD