How do you prevent nightmares?

I’ve been having a lot of nightmares recently. I try to fall asleep watching a funny movie or cartoon, or listening to soothing music, or reading a book before I get tired, but no matter what I’ve been having really intense nightmares. It’s getting to the point where I’m afraid to fall asleep because I don’t want to have a nightmare. Is there any way I can prevent them?

For the record, my daily life is not very stress-inducing so I don’t see this as some sort of manifestation of stress and anxiety, but the idea of having nightmares every night is quite stressful when bedtime comes.