Vibrating King Snake
 

I have a young adult Ruthvens king snake who is easy to handle and beautiful to look at. Sometimes, when I am holding her her muscles/body vibrates when she tenses up. Is this some kind of neurological issue? Anything to worry about? Or is this a harmless condition that some snakes have? Apart from this, she seems completely healthy and happy. Anybody have any insight into this condition? Thank you.