I literally experience a brain scrambling sensation what could this be?

Over the past few years I've had this sensation in my head that literally feels like my brain is being scrambled that's the only way i can describe it. Its not dizziness it always makes me stop what ever i'm doing and close my eyes and hold my head i feel unbalanced almost like ill fall over and then after about a minute it goes away and i get my barrings again. Its very uncomfortable and some times happens a few times a week other times it could be months before it happens again. Its happened both standing up or sitting down, its not related to getting up or sitting too fast or a change in light, i really cant find any correlations in the experiences. I'm an over all healthy 22 yr old male. Not over weight, I am a smoker, no health problems. Has anyone experienced this or know what it may be? I have not seen a doctor yet kinda nervous to go both for financial reasons and afraid that it may be something serious.