sleep apnea. Doctor told me some patients reported more vivid dreams, including nightmares.

similar to the one in Dr. Strangelove, though no one was riding the bomb in my dream.
I also had dreams of my teeth being loose in my jaws, ready to fall out.
Perhaps other odd ones I can't recall at present.

That was ca 15 years ago. I have used a C-PAP every night for ca 15 years and no longer have those dire-type dreams.
As a matter of fact, I no longer remember what I dream, though I may not be getting enough sleep each night (usually 61/2-7 hours.)

after awakening. The only reason I brought it up is something that surprised me after having a cardiologist check me out. One of the things he asked me is whether or not I had more vivid dreams, nightmares or dreams that seemed to take longer to dissipate upon awakening. I was kind of surprised to hear him ask that question, but it turned out to be on target somewhat. Anyway, I know that wasn't where your OP was heading, so I won't drag it out. Hopefully you will get answers that help.

I found that changing from a mask to a nasal pillow helped a lot. I think it has been about four years.

conscious enough at the time you're dreaming; you can stop it like a video, "rewind" back to where it started getting gnarly and demand it go in a direction YOU want. It can be done, I've done it. Sweet dreams!

For me, when I'm dreaming I generally have no clue I'm dreaming, just caught up in whatever is taking place.

The rare times I do become aware I'm dreaming, I don't seem to be able to do anything about it.

That's how I ended up in the locked psych ward last time.

Meds work remarkably well. Then I travel between alternate realities when I sleep or daydream. I have some control over that.