My dog does this too, and I doubt she’s had a single traumatic experience in her four years of life, all of which I’ve owned her for. Most the time, I’d say they’re probably just dreaming of chasing a cat or something. Dogs get really into their dreams, unless they’re audibly whimpering, I wouldn’t bother them. Occasionally my dog gets too into a dream and starts barking or whining, and I wake her up to stop her from making too much noise. But I don’t think it’s a PTSD or anxiety thing, it’s just a dream. People nowadays are too quick to diagnose a problem. Dogs, just like people, have nightmares occasionally. They sleep more on average then a human so they also have more nightmares on average. Dogs also don’t release the same chemicals or same amount of chemicals humans do, so they move in their dreams more often. Your dog is probably having a normal amount of nightmares that anyone has, but since she moves more and sleeps more then we do, it seems like a lot. Just let her be a dog.