It may be best to avoid Kundalini Yoga without the aid of an adept, or try to open the psychic centres. Not that you are doing this, but all God-men teach that the safest way is the way of the Heart; the devotional Path, do not rush the spiritual life.
I wish here to give you a larger answer so as to benefit you some. Purity is essential and the idea of service to all, prayer, exercise, self-control ... are all aids to purify the soul. In the spiritual life, it is never wise to jump from A to B. Purify the lower nature first,
Now for your question. Spiritual experiences can come as a very powerful force. In fact the divine force (called Grace) is always present and we are simply making ourselves receptive to it. The individual will go into a tranquil state, not a sleep mode. Meditation is vibrant and alive; not sleep.
But yes, the body may vibrate and head rock. do not be distracted, tell yourself that this is not what you want. use the 'not this' not that, approach and aim only for the goal. Forget the gifts that it sometimes bring with it. Much Love.