I am over weight and trying to loose some of it.
I have a desk bound vocation. When you breath you should do it by the diagphram, not the upper chest.
If you use the upper chest you will enhance your body system with toxins. I have found that even if the trousers are a good fit when i sit the belly becomes to big for the trousers. One should get adjustable waistline trousers. The other solution is to undo the trousers and sit like that. I can do this because I work from home.

By having a relaxed waistline I can then breath correctly and stay fresher and have no headache.

I also do this routine when driving and have much less incidence of tiredness at the wheel.

May be lives could be saved by undoing our trousers?

You should see a neurologist. This does not sound like vagal nerve stimulation. You may have a pinched nerve that would cause the symptoms you describe. A neurologist should be able to do a work up and tell you if there is anything going on.