If you want to send him to a kindergarten with good conditions and key kindergartens, it is better to go early. For example, when he is 3 years old and 3.5 years old, he has to take care of the class. You can send him off later and pick him up early at first, because the child is too young, unaccustomed and afraid in a strange place. You can guide him to like kindergarten. The advantage of going early is that he has enough time to adapt to kindergarten. If the place is not particularly good, I don't recommend sending him so early. If it were you. This will help him to enter the park in the future.
Habit formation will be of great help.