All children can have nightmares. It's not always after they see or hear something scary. Actually, children and especially babies, process new information they have gathered during the day at night while they are sleeping.
I taught my little one that she does not have to have bad dreams. Jesus gave us authority over bad dreams. I taught her to say this scripture. She is just four and has memorized it. Your child might not know what all of the words mean but you can explain the meaning of it. Basically, that all of your thoughts must line up with God.
2 Corinthians 10:5
"Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ..."
