My other dog was not neutered until he was about 10, and that was because an idiot vet decided to do it without any kind of request or permission on my part. The dog was never the same after that. All he wanted to do was sleep.
I am thinking that the neutering did not have anything to do with your dog wanting to sleep, I think that is age just caught up with him. My GSD has a strong drive and that hasn't changed since she has been fixed..she definitely does not sleep all the time
My golden is going to be 3 and he is just as focused and ready to go as the next golden.
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD