Upvote:1
Likely there is a subtle energy blockage around your elbows & shoulders so the lifting of the arms is to allow the energy to flow out of your arms and through your shoulders.
In Buddhism, we practise meditation on the natural ordinary breathing. This also leads to purification or healing of the body; where certain energies must flow so they can be released. Limbs can move to accommodate this.
Upvote:1
I am going to give you a neuroscientist answer, not a traditional Buddhist one.
Our mind relies on models of the world, and that includes our body, we basically live in a delusion or mirage. Normally this delusion coincides with reality, so we are not the wiser. Our brain constantly incorporates information from reality to keep our βdelusionβ (I.e., mental model) consistent. When it comes to our body most of this information comes from proprioception and skin nerve endings, but also vision.
This mechanism is made evident in phantom limb syndrome, alien hand syndrome, and in extreme cases body dysphoria. It can be easily explored with some basic experiments in normal individuals like the rubber hand illusion.
When we meditate we can directly interfere with these mechanisms, and our mental model of parts of the body can get disconnected from the information that those body parts are providing. To the extreme that our mental model can feel completely detached from the body.