I've seen shadows the size, rough shape and feel of cats on and off my whole life (I'm in my 40s now). I wondered if they were basically ghosts.
I also heard once from the astral travel community that cats can astral travel, which could imply a cat could be exploring in it's sleep as well. In either case it seems to need sensitivities to see them.
I have a cat and she reacts and yells at these. They stop as soon as I see them, and if she's yelling and I run to find her, hoping to see something, she stops, looks at me and acts like 'ok it's fine now' as soon as I get there. I only once might have seen a very fleeting shadow one time with that and I'm not certain about it.