It's normal behavior. The snake probably just needs to be handled a little more. My snake use to raise his back up and twitch along with hiss. He used to put on a big show but never bit. It's just the snakes way of saying to go away. My impression of snakes is that if you let them be recluses they will eventually become less tolerant. :/ that's why when my snake hisses or does that behavior I pick him up and hang out with him for five minutes or so to show him everything's all good. Since I started doing this he has since stopped all irritable type behaviors. I still don't mess with him in she'd though. I figure he has a right to be irritable in shed. Hope this helps.