Dog pees every time he gets excited

So we just got a dog from the shelter about a week ago. He’s a very sweet boy who is house broken except for occasional accidents when he gets super excited. He usually only does this when we come home or in the morning right before we take him outside. Otherwise, he never has accidents. I’m curious if I should worry about this being a medical thing like bladder issues or something. He is a young dog (around 2 years) Labrador/daushaund mix for reference.

Thanks!