I have a Dd who is nearly 5. Every night before bed she lies in the dark and babbles constantly for about half an hour, just a continuous dialog of randomness, bits of songs, noises, and lots of phonics spelling! Either myself or dh lie with her until she falls asleep, and if we ask her to be quiet she just carries on regardless.
This is constant and I always assumed it was her brain processing the day, but I'm curious to see if others do it too!
We have often wondered if she has been showing a few signs of autism for other reasons, and also wondered if this could be something seen more with autism.