A belated welcome to Fluther!

All I can tell you is that several of our dogs did the same thing, especially when Dad came home from a trip. Dad and the dog would end up on the floor and the dog would whimper as if carrying on their end of the conversation while he stroked and talked to it.

My guess is if the dog stays in position while being petted, it is a way of communication. If it were in pain, it would back away or run off.

I think that he likes it and is overcome with emotion. Try giving him a treat while you are petting him. He probably can’t whimper and eat at the same time.

My dog did this too, I always imagined her saying “I love you sooo much!”.

How old is your dog? Does it suffer from arthritis? Are you guys petting him too hard? If he’s a new pet he may have been abused previously and never knew when his master was going to go from loving to abusive. I would think the whimpering means he is either in pain or frightened. Does he ever turn over for a belly rub?
My sisters dog whines sometimes when petted near her rear because she has a bad leg and arthritis. She’s only 3 years old.

I would definitely analyze where he’s petted. If it appears to not be physical, then it might be generally emotional (saying “I miss you”, “Thank you”, or maybe something not so pleasant). Personally, my dogs don’t do this, they just pant gently.

My dog does that when I give him a rawhide chew. I interpret that as “I’m not worthy, I’m not worthy!” Then he’ll bury it until it gets soft and dig it out later to chew up.

Are you sure he’s not moaning with pleasure?

If that’s definitely not the case, did he come from an abused home and he is afraid of a hand that approaches from above rather than below? Try rubbing under his chin.

If all this isn’t applicable, maybe he has a skin condition and needs to see a vet.