The topic of unconsciousness is actually discussed by shankara chariand the brahma sutra. The restfulness which is experienced in deep sleep belongs to deep sleep only. Is not there anywhere else. So it cannot be brahman, which is always there. It's impermanent. Some people have day dreams, some people have koma and others are knocked unconscious.
Question and Answer session lead by Swami Sarvapriyananda as part of a spiritual retreat at the Vedanta Society of New York on Mar 25th, 2018.