Do children cry in their sleep?
Most certainly not. Nothing is wrong. There are no needs. There is no danger.
They rest peacefully.
What happens when they resume waking consciousness?
Mental activity resumes. They perceive themselves as a singular 'I' that will not survive without doing something.
This is where the majority of a child's cringe-inducing wails arise from. Their ego that feels separate, afraid, and powerless--that demands attention from the outside world to ease its pain.
(Note to parents: No amount of coddling your child's ego will do him any good. In fact, you strengthen the ego by coddling it.)
It's really wonderful, children do not know how yet to mask their egos--so we get to see its workings in full, unadorned glory.
Ever find it odd no other creature in Nature makes such a disregulating noise as the child's manic scream? No other creature is as emotionally fragile?
Children go from happy to sad about every 5 minutes. Sad when ego doesn't get what it wants, happy when it does (for a short while).
Something unnatural is happening, the ego is unnatural.
See that we never grow out of this pattern of crying to get something we want--we just use different tactics, but they all revolve around using negativity (or positivity) to manipulate reality to feel better. And how we're only happy for awhile, while we have the something we want.
Does any of this occur during sleep? Do we have problems? Needs? Cares?
When are you the most at ease? When you are doing nothing. Wanting nothing. Needing nothing. Being perfectly still.
When the mind is silent, and ego, for a time, is disregarded. Now we know why the goal of meditation and process itself resembles sleep in every respect, and why Ramana Maharshi said your ultimate goal was to maintain sleep consciousness while awake.
You're still you when sleeping. The experience of reality has changed (for the better), but the experiencer remains the same.
With so much talk of waking up, what we really need to do is shhhhh ourselves to sleep. And realize, if we are fully cared for during sleep, we are cared for while awake.