you mean like scooting his butt on the carpet? in a comical, hysterical way? i have a clip somewhere i caught on tape of a friend's maltese doing it! it's hilarious... lol
they could "scoot" for various reasons, and youre right about getting an answer from the vet to check it out.
it could be worms/parasite, it could be that they need to get their anal gland expressed (usually when you get your dog groomed, the groomer will do it for you.) or it could simply be that they have some fecal matter stuck on there, and they're trying to get it unstuck.
whatever it is, by him scooting his butt across the ground, he is trying to get some relief, so its great your going to get a vet to check it out!
dont they look hilarious doing it though?