The most common causes of occasional vomiting are probably the inflammatory bowel diseases and functional obstructions of the pylorus (the muscular valve between the stomach and the intestines). Intestinal parasites, ulcers, liver and kidney disease and other diseases can lead to occasional vomiting. Indiscreet eating habits such as eating foods that may be spoiled, eating to much at once, eating objects not meant to be eaten like rocks and other eating habits that can irritate the digestive tract probably account for a number of cases of occasional vomiting as well. You should discuss this further with your VET.