We've met a few dogs out on walks who have developed the same snaking... both cockers... owners have said it's been since lock down and the unsettling amount of people out and about....?
Hope he's ok xxxx
don't know if this is related, but paris sorta does this too. at any rate she pants, her heart beats so hard you can see herr diaphragm move. i thought it might be the heat? sometimes, when she drinks wter, she coughs like she needs to hack up a hair ball.
My cockapoo started doing that along with increased panting around the are of 8. The vet said it was an idicator of pain. Turned out he had arthritis and was really good at hiding his pain. Got him on meds that helped immensely. He lived to be 13.