Sleep Meditation

It happens that someone arrives to find himself/herself being aroused from sleep after sitting or reclining for meditation. This happens with the person having little or no idea of how the sleep state began or was terminated. There may be a clutching in the mind to figure how the sleep overtook the self.

Was the individual targeted by a drowsy energy which had the power to overtake the objective attitude of the self.? Who is the self? Or rather, what is the self? Is it a composite of perpetual subjectivity and fractional blinking objectivity but with the blinker being controlled by something/someone else?

While in meditation, where somehow one falls asleep, what is the sequence of existential events which occur before the objective part of the self, loses track of itself and everything else?

A yogi may study the drowsy state which proliferates through the psyche just before there is loss of objectivity. Where does that drowsy energy emerge from? How does it suspend objectivity.

Why after some sleep states, there is memory of what occurred just prior to the onset of sleep; while in some other sleep states, there is no memory, and for a time, for moments or minutes, the self finds itself to be existing afresh, being radiant but with no history for a reference.