The body moving without the usual sense of volition
The body moves without the usual sense of conscious direction: kriyas, rolling, rocking, mudra-like gestures, sudden jerks. These movements often accompany kundalini activity and can persist for months or years.
What makes these accounts distinctive is the lack of volition: the person describes watching their body move rather than moving it. Some find this frightening; others describe it as a welcome release of something held in the body.
And Kriyas are spontaneous movements of Kundalini that are aimed at clearing the subtle body, the physical body of any kind of impediments that prevent us from knowing the fullness of our own divine nature and seeing that divinity in everyone in all the world.
And in TRE you can control it, you can stop and start the spontaneous movement and so that gives you a sense of, ah yes, my body knows what to do, my body knows how to heal itself.
Yes, so a kriya is, easiest to understand it is a spontaneous movement.
So kriyas are movement of the energy, the Shakti, the power of consciousness.