First time poster here, hope this is in the right place!
From the moment we got our GSD (now 7 months old) he has been extremely placid for a puppy. He sleeps almost all the time unless he's out on a walk. I thought when he was younger that this was maybe due to growth spurts but it's been the same way since. He rarely bothers us to play and sometimes when we try to get him to play he actually stays lying down on his bed while playing tug of war, we really have to coax him to get up.
There are obviously times when he gets extremely hyper (the way you expect puppies would be), but this doesn't happen all that often. We mentioned it to the vet when we first got him but he advised that he is perfect and that we are lucky to have such a placid puppy.
His seems lazy/lethargic and I was thinking maybe this is just his personality but is it really that normal for a puppy to sleep all day long unless disturbed?
What kind of games do you play with him? I have one on the couch potato side, but she will play. She's picky about what she'll fetch. The ball has to be the right size and she won't even raise an eyebrow for a frisbee. You might just need to try different things to see what he likes.