Not hibernation, and not sleeping. Just chilling in his hide and conserving energy. You can tell the difference between a sleeping snake and an awake one if you pick up the hide. An awake one will be immediately alert and oriented. An asleep one will be non-reactive and may startle if you disturb it. Even when sleeping more and eating less during the winter months, this is not true hibernation (brumation, in reptiles). That would involve a suppression of metabolic activity in order to prepare for a long winter, which they don't have in their native home in Africa.