#1 Stress due to husbandry related issues, main cause to large of an enclosure and over handling.

#2 Because he is a baby, keep in mind that young individuals tend to appear more nippy it is directly linked to their size and the fact that they see you as a predator hence the reason why they are being defensive.

#3 Not feeding enough.

A description of you enclosure, size of the enclosure, size of the animal, temps provided, humidity provided, how often the animal is being handled, food size offered and how often etc, would really help narrow it down,