I do have a lot of experience with this, but only second-hand. My dad has increasing problems with this. For him, it's mostly when he thinks about someone from the past or tells an old story. I'm not sure if it's a symptom of his Parkinson's disease, or if it's from one of the many medications he has to take, or if it's just something that's happening for no known reason, like it sounds like you might be dealing with. I know he gets embarrassed by it. His doctor even tried putting him on an anti-depressant but he didn't take it for long. Not sure why.
It's hard seeing my dad cry. He's one of those "tough as nails" kind of men. I remember having to help him patch up deep gashes he would get from working in his mechanic shop, and he wouldn't bat an eye. I think it hurt me more than it hurt him.
So I don't have a clue what to tell you, I can only commiserate to some extent. But if in the future you do learn something about it that helps, I sure would appreciate it if you'd share it with me.
:grouphug: