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Consciousness is often said to disappear in deep, dreamless sleep. We argue that this assumption is oversimplified. Unless dreamless sleep is defined as unconscious from the outset there are good empirical and theoretical reasons for saying that a range of different types of sleep experience, some of which are distinct from dreaming, can occur in all stages of sleep.
Pubmed Articles
Does Consciousness Disappear in Dreamless Sleep?
Sciencealert Article We Were Wrong About Consciousness Disappearing in Dreamless Sleep, Say Scientists
It wasn’t dreamless, you just weren’t remembering your dreams. If your sleep was truly dreamless for a lengthy period of time you’d be dead.
Often simply changing your sleeping habits in any significant way is enough to get you to start remembering dreams. That’s because you need to wake up “unexpectedly” in the middle of a REM sleep phase to have a chance to form memories of them. Normally your brain has its memory-forming mechanism disengaged during REM sleep because there’s no good reason to remember that stuff - it’s just a side effect of a mental housekeeping routine.
You can also “train” yourself to remember dreams more often, to some degree, by trying to record a dream journal or otherwise forcing your brain to lay down some memories of those dreams the moment you wake up and they’re still present in your short-term memory.