Why do I have issues when going out to eat?

For the past few months I have had problems when eating at restaurants. Everytime I go, I order an appetizer and I am fine. I share it and enjoy it and don't feel sick at all. Then when the food is about to come I usually start feeling a little ill or anxious. When it comes, I can take a few bites but then I always feel full and sometimes nauseous. I then try to occupy myself by drinking water but nausea and anxiety always start to hit me. I get shivers and feel very cold and get erflies in my stomach and my throat feels tight. I then have to use the bathroom (#1 and #2) and then feel EXTREMELY thirsty afterwards but cannot seem to satisfy it. By then, everyone else is done eating but I can hardly touch my food. I get the shakes in my legs, too. I then feel panicked and want to leave and can't seem to get out soon enough. I usually feel a little nauseous for the rest of the night and have mild anxiety. I don't get social anxiety elsewhere. Anyone know what I mean?