AllThisIsThat
It's all good - I've experienced radical involuntary movement experiences many times since I started practicing SFQ and while I was a bit frightened to start with, I trusted the Master and the universal energy - the energy is breaking up or travelling through blockages, realigning the skeletal structure and organs and much, much, more.
As IAM2 says - trust the energy, stay with the flow, observe, enjoy but don't get attached to the experiences. As your body continues to heal, the quality and the feel of the energy and experiences will change again - you have much to look forward to.
It's a magical thing SFQ, alchemy is happening inside your body, mind and spirit and it's beyond anything anyone else can do for you.
