Ok so I'm going to sound like a real mad cat lady now, but can cats have nightmares do you think?
We have adopted two cats a while back and they have a pretty chilled life... eat, sleep, repeat etc - they have a microchip cat flap so can come and go at will, but never venture far, I WFH so they are rarely on their own, we have feliway plug-ins etc, but the more timid of the two seems to have nightmares.
He's asleep behind me on the radiator shelf and he is mewing and twitching like he is distressed.
They were worshipped by their original owners who had them from kittens but had to put them in a shelter when they had to emigrate, so they spent a very unhappy year in a shelter before we got them.
Watch a dog sleeping in front of the fire of a night - they mouth gently and twitch, their front paws go etc etc. Cats are much the same, maybe just a little lower key. Who knows what they're dreaming about though?