It is good that you plan to see a specialist who can give you insight to the root of the problem. Is it a panic attack? Do you have this problem at certain places/ restaurants more than others?

Since the nausea is psychological, by not eating anything you are basically telling yourself that it is ok not to eat. I have often gotten nauseated just by thinking of leaving the house to go to a restaurant and often force myself to eat something so it doesn't get worse.

Some short term things you can do is 1. practice meditation/breathing in a comfortable place in your room so then you can apply what you have learned in an uncomfortable setting. 2. Another idea is to slow down so you do not get anxious. Try eating a couple bites and putting the utensil down for a few minutes and tell yourself that you will be ok. Then when you feel ready, try to take a few more bites. This can positively reinforce that eating is not a negative behavior if you don't let it. 3. Try eating light foods that will be easier to eat like fruit or salad. Eating a big meal can make it harder to cope.

Hope this helps