In some cases this type of behavior as well as food refusal is linked to stress can be something else too, also remember that young animal tend to be more defensive than larger individuals.

Can you give us some details

Animal size, enclosure size, temps (how you measure them and with what type of device), humidity, hides (number, size), how often you are handling the animal, how often you have been feeding it, what prey size and anything else that might be relevant.