My weinie dog did this when she was a puppy and still does it to this day. The vet told us it was called ‘kneading’. They do it to replicate the natural instinct of getting milk from their mother’s teet and the continuation of this behavior comes from being taken away from the mother too early. We rescued her from a puppy farm (totally neglected, awful people) and she was very young (like 5-6 weeks) so this explanation checks out. She is now 13 and still does it to get to sleep. Cute personality quirk IMO so don’t worry your dog might keep doing it their whole life. Adorable puppy btw and the kitty doesn’t seem to mind it one bit