I'll have to agree with Guest here. I've had it 5 times in the last year, mildly, thank goodness. It's usually related to a respiratory infection for me. My neurologist doesn't think it's related to my MS, but certainly something I'm watching. If you don't like what your doctor says, ask another, then another, etc. Good luck. This has got to be frustrating. Others have described it to me as like seasickness.