Hi and congratulations on your new puppy!! 8 weeks is still very young. I think its very normal for them to sleep alot more then play at his age. Its a good thing you got him to the vet, and personally from my experience with Sunni, she is quieter after she has a vet visit, especially for shots. I think it was about 10 -11 weeks before she became very playful and fiesty, and there has been no turning back!! Give him a little time and lots of snuggle time, I'm sure he will start being a more active puppy in a week or so
Best of luck!!