Its is also stress induced.
I know a couple people that swear their spider never has and will never show signs of a wobble....... LoL
A little stress and guess what? One shows it when feeding, while getting ready to strike there is a minor visible wobble but not what the owner noticed.
Most people think of a wobble as the wild corckscrewing you see on all the you tube videos. It can be as slight as an improper head tilt.