I have had vivid nightmares before. If you have PTSD, there is a medication called Minipress that you can take to get rid of the nightmares. Other than that, make sure you feel soothed when you go to sleep. Don't watch anything violent on TV at night or read anything disturbing. You can look on YouTube for videos on guided imagery. It can help calm you and put peaceful pictures in your head before you fall asleep.