12week old shitzu tripping over a lot

Question
hyi

dad has bought 2male shitzu,pups they are fully vaccinated ,they are both from same litter 1 is very strong the other is just has big,but for some reason it seems to be weak on his balance causing him to trip over a lot .then he just lays down to playfight he does not seem to be in any pain but i feel there is something wrong as has this is happening all the time any ideas please

Answer
Some dogs, like people, are not as strong as others. But it might not be his balance at all, but it could be his heart or something causing his stamina to be weak.

He should be seen by the vet. He could have a heart murmur or a defect that is causing this. He could have had a virus that affects his balance in his inner ear.

There are so many causes that he really needs to see a vet to determine what is wrong.