I get a weird vibration feeling the the back top of my head for a few seconds where my eyes unfocus and i experience some vertigo. what is it?

Too vague to know: First of all, this part of the website doesn't answer the question "What is it?" That's diagnosis, which (read the disclaimer) is something that the docs who answer these questions don't do. Second, the vertigo SUGGESTS (that's as far as I'll go) an inner-ear problem. See your doctor. If he/she can't figure it out, referral to an ORL doc may be considered.