As Albert said, it's good not to handle until they are eating regularly. Once they're settled in, IMO it's fine to handle daily unless they've just eaten (I handle for short periods of time basically to check the snake over and make sure nothing's wrong; I think extensive handling, like more than 15 minutes or so has the potential to stress them out).
Also, babies are going to be more nervous about handling than adults generally, and will get stressed more quickly and tend to be more nippy. They usually grow out of it though.