Burmese biting for unknown reason

[lambert]

I'm just curious on why my Burm, who is handled all the time, bit someone out of the blue today for no real apparent reason. He had been fed just three days ago, there wasn't anything that I can think of that startled him. He didn't pull back and strike, just like he normally does, because he is 6 feet long, moves from person to person, and just no strike, bit my friend. He has never done this before and it is really out of character for him!! Any clues or ideas, aside from the normal, "he's a snake, and snakes bite"???