He is an individual with his own personality. Haven't you known adults who hate big cocktail parties? There is no abnormality in being who he is.
Thanks Sandman for the response. I feel the same way you do. He is just 4. Since he is a Fall birthday, we are going to hold him back from kindergarten anyways. So, I will see how he is in school next year before I consider having him evaluated.
What commands does he zone out to? They are all sitting on the rug - and the command is? It may be that he is more interested in the person next to him and tunes out the teacher. If this really worries you, I would be at the back of the class and watching during that time.
The other thought is that if he is bilingual, it is not unusual to zone out in your secondary language if you have the chance - don't know if this would apply or not.
Final thought is how old are the other kids? If the group around him is older, that can be enough to quiet you down.
Don't know if this is enough to help. But after years in education, I would say (without more information) - don't worry about it. Best wishes.