Hi Jay,
I found an old thread in abuse&bullying support that might be helpful
nightmare help thread
If your nightmares aren't related to past abuse then it might not all be relevant but there should be some helpful bits. I say this as I don't know your history and I in no way expect you to disclose said history unless you chose to.
Things that help me with night mares include making my bedroom feel safe before going to sleep. Simple things like closing the door, leaving a nightlight on if I am on edge, having cuddly toys/ plushies in bed with me. I have sometimes found doing some grounding before sleeping helpful as well to get my mind in a more settled state.