I woke up years ago in the middle of a panic attack. I know it was a reaction to some difficult changes I was dealing with. But the room was so dark and I was so out of it that I couldn't tell which way was up and which way was down, and I was frantic trying to get to the light switch. Ever since then, I've always slept with some sort of light coming into the room, whether it's a night-light or a hall light or light from a streetlamp coming through an intentionally partially-closed window shade.

Do you watch many crime programs, or Science fiction ones before bed? Do you use the cell phone,tablet or computer before staring for bed?

I saw a YouTube video presented by two sleep doctors. Sorry I didn’t save it so can’t post the link but they said that nightmares are associated with having the room too warm. Cool sleeping environment is best. It sounds strange but is consistent with my experience. When I wake from nightmares the room is always too hot so I think there might be something to it.

lot of nightmares, but NIGHTLY hallucinations, which are always horrible (fire, soiders, intruders, etc). I have always had a tendency, but migraine meds kicked it up to a daily event. Poor trade, but the head pain is too severe and constant to go without.

For most of my life I seldom had dreams, let alone nightmares, that I remembered or was aware of. When I had my heart issue almost two years ago, the doctor put me on several medications such as statin, Plavix and another blood thnner. Ever since I have been on these medications I have wild and vivid dreams pretty much nightly. They are not really nightmares, but can be exhausting, since most of them involve being chased, chasing, frustrations, and other activities that leave me waking up in a sweat or exasperated. And I can even get up and go to the bathroom sometimes and go right back into the dream when I return to bed. I tried not taking one medication at a time for five days to see if it made a difference, but it didn't. The only good thing is there are occasional sexy dreams, that though they leave me frustrated, give me a bit of joy too!

There is most likely an unresolved and/or ongoing conflict in your mind that "sleeping" allows to float to the surface. If you can remember snippets (write them down immediately after waking up from one!...pen & paper at the bedside!), you may be able to ferret it out & that will make it go away.
Be aware it does not have to be something major, it may be something "trivial" as your sleeping brain has no judgement! Best wishes!