Vibrating brain and dizzy?

This happened with my last pregnancy, I’m 6 weeks and will be sitting down and occasionally my head will start “buzzing” like vibrating and I feel like I’m about to faint, I have to sit and focus a minute to not pass out and it goes away. Literally like 5-6 seconds and it’s gone. I didn’t stand up or anything it’s so strange? It’s scary I get so scared.