Toys?!?! No thanks

Vet said he's okay? Eats well and drinks well?

I can see why you would worry, I love the crazy puppies. On the other hand you have been given the gift of the easy puppy. I've not yet met one myself, just heard rumors

I'd take him to petsmart, see if there is not some toy that would really get him interested,, I'd start tossing toys around, maybe you can find that "perfect" noise. I would also do the happy jumping acting like an idiot to see if I could get my pup excited, with some yummy treats in my hand.

If you are truly blessed with a calm puppy, embrace it, try doing therapy with him and OB, maybe rally or agility when he is old enough will pique his interest.

I don't have this myself so I can't give any real advice, just what I would start with if I were concerned

I spent the first two months of Shadow's time with us worrying because he seemed so much less energetic than I thought a puppy should be. He didn't play much with toys and spent a great deal of time sleeping. He was fine, according to the vet so I guess all that growing he was doing back then took up most of his energy. He's now 8 months old and in great shape with plenty of energy when we're out and around but very laid back and mellow in the house. We can get him to play with us at the drop of a hat but if we're doing other things he pretty much just hangs out, chewing on his chew stuff. I suppose we have been really lucky with him being so mellow... my daughter tells me horror stories of her pit/boxer mix puppy and how he terrorizes the whole household with his endless energy. All I can say is better her than me?