I began experiencing kriya simultaneously with a Kundalini awakening. Both occurred as the result of about 4 months of daily breath-focuses walking meditation. The kundalini is now constantly awake, feeling the distinct energy flow in my whole body even as I type this, and it does follow, for the most part, the classical descriptions of the left, right, and central channels, and the numerous chakras. But the background awareness of that energy is different than my experience with it when I stop give myself to dedicated meditation sessions.
When I begin to meditate, I focus solely on the flow of energy. I make no attempt to control the flow, because it has a mind of its own, and knows where it needs to go. The kriya begin almost instantly upon starting meditation, usually with movement of my hands and/or feet. I do these sessions lying on my back. The hands seem to be used for manipulation of the energy, focusing it and moving it. Sometimes the kriya are strange hand mudras, or flourishing whole arm gestures. Many times I will be directed into very complex or difficult yoga positions. Sometimes my movements resemble Tai Chi. I do not direct these movements, only allow them and watch them. But I am completely able to stop them if I wish, but why would I do that? It is clear to me now that the Kundalini is working a healing and transforming process.
I have found that this experience is understood as a natural part of Bhuddist practice, especially in Tibetan Vajrayana, but it is hidden, an esoteric practice reserved for higher level initiates. An American named William Bodri wrote a book about this kundalini energy progression called The Little Book of Herculese. Another book by Master Nan called The Tao of Longevity is also about this. Unfortunately most American Buddhist frown upon kundalini as just another phenomena that should be ignored. That kind of attitude is really just a display of ignorance.