Melchior Dombrowski
Melchior Dombrowski voted up Angela Anthony's answer

Dramamine is an over the counter medication you can use for motion sickness....another one is also called antivert or meclizine. Just be sure to take the medication about a half hour before you leave and follow the directions on the package. If you already have nausea, ginger will help ease it.

Melchior Dombrowski
Melchior Dombrowski voted up Gator Blu's answer

If it only happens sometimes, I would presume it has to do with sinus pressure on the inner ear. Try taking an anithistamine.