I think it's more about Andre learning how to pace himself for longer stretches. Andre is nearly 300 pounds and frequently sprinting on offense and defense, he jumps higher than his opponent all the time on offense and defense. Andre was a 300 pound teenager last year who was so athletically elite he made a habit of chasing down his own misses for scores. Usually multiple times per game with great consistency, sorta like uh... Moses Malone.
Give him until at least the start of the regular season before you question his "conditioning". You know who else would be winded in summer league? Every single starting Center in the NBA because they are resting and recovering from last year still...
Clearly, he is not out of shape.

He just needs learn how to be a 7'0" 300 pound big man in the NBA. Yeah, sure... Taking the ball past half court as PG randomly just because you can and then driving to the basket because you know you can dunk is very, very exciting and SCARY freakish impressive... but probably not a good idea when you are 300 pounds.