Motion sickness
Dizziness and nausea is frequently caused by unusual physical motion (or perceived motion) - e.g. air sickness, sea sickness, car sickness, VR simulation sickness etc etc.
There are three commonly-documented 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 main 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 dizziness-inducing effects.
The second theory is the 'Nystagmus Hypothesis' which is explained here in : The possible role of nystagmus in motion sickness: A hypothesis 
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."
Also see : Mal de debarquementplugin-autotooltip__plain plugin-autotooltip_bigMal de debarquement
Mal de debarquement Syndrome (MdDS) is associated with Motion sickness (i.e. sickness caused by the movement of sea, air and land travel) except that it's experienced after the individual returns to the stability of dry land.
It's a persistent form of 'Land sickness' which many people experience for short periods after disembarking from a voyage.