When the igneous serpent of our magical powers awakens, the devotee passes six short but unforgettable experiences. These six experiences are: Divine happiness, a trembling body or body parts, astral projection, spiritual voluptuousness, coccyx pain, dizzy spells in conjunction with deep sleep filled with spiritual brightness. - The Yellow Book
However, there are other more common potential causes. Generally speaking, it is not wise to assume that physical symptoms indicate kundalini activity, since physical symptoms are totally unreliable.