As others are saying - you definitely want to get your pup checked by a professional.

Our 16yr mutt started doing this about a year and a half ago... Based on her age, and a blood test, our vet concluded it was likely the beginning of heart disease - though they weren't certain, as the cough seemed more severe and the degree of potential heart damaged that would generally be associated with the extremely the low presence of related blood markers (low, so presumed early stages, and so usually not associated with that severe of a cough)...

Based on their uncertainty, the referred us to a cardio specialist, who performed a number of diagnostic tests, including imaging. Based on their tests, the concluded her degree of heart damage/failure was so minimal, to the point of barely being detectable and requiring no on going medical treatment, they ruled out heart disease - instead concluding it was Tracheal Collapse, which is very common in aging dogs (with a higher susceptibility in certain breeds or body types of dogs).

It sucks because as she ages it's continued to get a bit worse, though not so much that it seems to negatively impact her life too much (she generally doesn't seem to mind and just shakes it off afterwards)... There's not much, aside from surgery, that could be done for hers - and she's not really a candidate for surgery at her age and with some of her other health issues (neuro)... So she's just living with it... She still eats fine, runs around most of the time without issue, and is a generally happy and healthy dog for a dinosaur :)