Change in behaviour

Any sudden change merits a vet check - at his age, probably including blood work.

Dogs are very stoic about showing pain, but it can cause behaviour changes so a thorough check is a first step.

 

Having had the health check, could there be static shock anywhere in the home or car? Are there new computer games causing noise audible to dogs but not humans? New kitchen appliance that vibrates or squeals? Same for close neighbours - when I lived in a thin-walled newbuild, my neighbour's dog used to freak out when my washing machine went into the spin cycle. That was easily fixed, and I hope your dog's problem is too.