I find the Universe one the best one for me. The one for Humankind or Earth can be unsettling sometimes (mostly the intros in my experience) but I don't have problems with uncomfortable dreams really so I don't mind. But from my experience if there's something that could give you a bad dream it's only in the into.

The History channels:

• History of the Universe
  • Found them on this channel
• History of the Earth
• History of Humankind
  • This is their new channel that they started just a short while ago.

It's really good long form fomat. You don't have to watch anything and just listen. It's long enough for me to fall asleep and not hear the whole video so next night I just go close enough to the end of what I heard/remember I heard and just continue listening. I don't mind relistening at all - I always miss something so I always learn something new.

Edit: the awesome thing is that these videos are told basically like a story. The narrator's voice is calming, there are no loud noises or anything. He really tells it like a good night story.