TonyK, it could be due to passerby’s that irritates it and keep knocking on the glass.
I have noticed that pet shops’ reps are always a bit more agro, and you mentioned it is a hatchling.
Therefore it will be until it is a bit older, bigger and handled more.
It could be his/her personality, but one cannot generalise due to one hatchling, in a pet shop, not being handled. (TonyK, statement is not reflected at you
)