When snakes are having an attitude where they are always constantly nippy and biting, that means that they are either stressed or hungry. Snakes are very prone to becoming stressed, and it's so very easy for them to become stressed, and what triggers their stress can be a number of things, but the main reasons how they get stressed are:
1- improper husbandry (not having the correct items/temps needed for that specific species of snake)
2- too much/too long of handling (handling for long periods of time or being taken out multiple times)

When snakes are fed small meals that don't fill them up, they will be on the hunt for food a lot of the time. They will even come out during the day time searching for something to eat. So if your feeding your snake too little of meals, you may want to go a size larger. Go by this rule when feeding: feed the snake a mouse about the same size as the middle part of the snake's body.