Lethargic puppies are never a good thing. Especially with a shelter puppy, a million things could be wrong. From a cold to a virus to just being content that he is out of the shelter and is happy he can sleep in peace 😉. On this forum you will not get any medical advise, for many reasons. He needs to go to a vet (well, you knew that). If you think you can wait until tomorrow (now just a 15 hours away) then you can do that. If he is showing signs other then lethargy find a 24 hr animal hospital (vomiting, diarrhea, weakness). Good luck with your puppy. I'm sorry to hear that he is not doing well. Keep us posted.
-make sure he is drinking, force him with a syringe if you have to (just water, not milk or anything)
