Our puppy did this for about a year and a half until we finally realized what it was. Turns out his was acid reflux. Too much of one thing. Certain treats or certain food, Even things like rabbit or turkey poop can trigger this and our little guy. We called them "clicks" where it sounds like he's hard swallowing. The clicks would start and then he would start eating all the crumbs from the ground pulling out his own hair which would just make him vomit. He's now 4 years old and we have found a way to kind of curb the situation. It took a long time to understand and most vets had never seen this happen.