I think you were starting to have an Astral Experience. Everyone has an astral body that they can seperate from their physical body. When you felt the sensation of movement that didn't occur physically your astral body was trying to exit your physical body. You should learn to contol these astral movements so that you can leave you'r body and enter your astral body. Advantages of astral projection are
1. Being on the astral plane(also called the spirit world or such)
2. Journeying through this beautiful astral plane.
3. You can fly so high that you can end up in space!!!

Posted By Dream Child