Often, your Kundalini will prefer to work on you when you are asleep, and your ego mind is turned off and cannot offer resistance or interfere. So, you may find yourself sometimes becoming inexplicably sleepy at odd times.
The best thing to do, is to surrender to this and take a short nap. Often 15 minutes of sleep will be enough to give your unconscious time to do a re-set of your energy body and you will wake feeling much refreshed. It is like hitting the "re-set" button of your computer: it shuts down briefly and re-boots, starting fresh.
This especially happens when someone is doing some sort of energy work, like energy based healing or using empathy. The unconscious wants to clear any karmic debris stirred up or taken on from someone else, and make the best use of the energy that is available. I always suggest my clients make time for a nap after a session.
Sometimes you may find yourself in a phase where you seem to sleep a lot, this means there is a lot of karma processing going on. You may also experience spontaneous prolonged wakefulness during different phases of your process. These effects are perfectly normal, so just allow them.
You may also experience a phase where you wake up regularly at 3am, with kriyas or without them, often after experiencing some sort of symbolic dream. The timing has to do with sleep cycles. Often, when you awake at 3am you will not wake up fully, you will remain in that twilight zone state, similar to hypnosis, where the veil is thin and it is easy for the conscious and unconscious minds to communicate with each other.
There is a higher than average incidence of chronic fatigue syndrome among awakened people. My observation is that chronic fatigue seems to occur most often in people who lead very busy, "having it all" type lifestyles, and to those who spend most of their energy doing what other people want, instead of taking care of themselves. The CFS appears to *force* them to slow down, turn inward and take care of themselves. I have also seen it happening as a result of a Reiki initiation. Reiki is not compatable with Kundalini, but initiations can be reversed.
Observe yourself; sometimes fatigue can be a side effect of a subtle food allergy or environmental toxin.
Disclaimer: I am not a medical doctor. Always seek the advice of a physician with any unusual symptoms, especially if they persist.