This could be the opening of the chakra. This is a conscious doorway to the lucid dream state, or astral projection.
It could also be Kundalini Rise it usually rises as a result of different events or processes. First, and most likely, is the strengthening of the subtle energy system.
Everyone has their own individual energy vibration. The faster the energy the faster the vibration. It could also come along with tingling in your hands and the sound off a hissing, like a snake.
Love and Light,