Yes, it is entirely normal....for pussies!!! lol just teasin', seriously though, yes what you are experiencing is something experienced by almost everyone. Don't have a heavy meal before your squat/leg workouts. There isn't really a whole lot you can do to stop the nausea to a great degree besides backing off in intensity slightly. And if you do throw up, its ok just make sure to wash your mouth out afterwards, the acids in your tum tum are hell on your teeth, hence the reason why so many sufferers of bulimia have horrendous cavities.
kind regards,
jeremy