How to get the kundalini to awaken... again?

When I was younger and feeling very much in love and lost.... I repeated the word numb over and over in my mind while performing circular breathing (pranyama). My spine began to vibrate ever so slowly at the base moving upwards. It then increased in speed and frequency until my entire spine was vibrating up through my crown... my mind went completely blank... a vision became apparent.... and I began to what I can only describe as astral project..... until I "turned around" out of fear and woke myself up.... Why did this occur in such an order.... and how to repeat it?