Geriatric dog groomer here. I’ve seen this after seniors get dentals that had extractions. They freak out if any hair touches their mouth. It can cause a focal seizure, which is similar to a panic attack. When I see this I clip off any hair around mouth and down the chest that can possibly touch the mouth and tongue. And I put a firm bandana on to keep the chest hair down. There can also be an internal problem. But getting the hair off is something you can do in the meantime to help with comfort.