Haven't been tagged by mine yet, he's docile as can be when being held. He has struck the glass a time or two at quick gestures - usually pointing or hand gestures at eye level-can't smell through the glass....has happened three times total. I just assume he's a little cranky and just leave him be.
I figure if you read the animal accurately you can minimize and possibly eliminate spastic moments. Keep in mind that in a pet store environment the animal usually is completely lacking any kind of feeling of security and are handled randomly many times a day. That would make me a little snappy, too.
Like above posts say, neonates can be a little jumpy, but also keep in mind that with a stable home and security needs met these traits can typically be eliminated. Unless you just wind up with a nippy snake..........half the fun is finding out! lol