My B. Albopilosum was vibrating?

I saw the strangest behavior the other day and maybe one of you has seen it?

I have a lot of dirt for my girl to dig so her legs can reach the lid, I was checking on my Ts when I see her.. Vibrating.

She was sticking her leg through a vent hole, opening and closing her fangs, and shaking vigorously, almost like vibrating.

I touched her leg and she stopped and pulled her leg out, I have never seen this happen.

Similar experience anyone?