Dizziness and nausea is frequently caused by unusual physical motion (or perceived motion) - e.g. air sickness, car sickness, simulation sickness etc etc.
Summing them up, there are (at least) three versions :
· Caused by motion that is felt but not seen
· Caused by motion that is seen but not felt
· Caused when both systems detect motion but they do not correspond
There are currently two theories about why this might happen :
The first is that it's a mistaken defence against neurotoxins, in other words an emetic effect designed to eliminate ingested toxins which (can) have very similar effects.
The second theory is the 'Nystagmus Hypothesis' which is explained here :
in Aviation Space and Environmental Medicine 65(11):1032-5 · December 1994. In which the authors note, however ;
“[…] the mechanism by which vestibular stimulation ultimately leads to motion-sickness signs and symptoms, including emesis, has by no means been established.”