Michael's drowsiness is an example of an altered state of consciousness that occurs "spontaneously".
An altered state of consciousness is any condition which is altogether not the same as a typical waking state.
An altered state of consciousness might be characterized as a brief change in the general example of emotional experience, with the end goal that the individual trusts that his or her psychological working is particularly not the same as certain general standards for his or her ordinary waking condition of consciousness.