Cats, as you’re witnessing, have a much more sensitive vomiting reflex than we do, so it isn’t unusual for cats to vomit when they don’t appear sick. I assume your cat has a healthy, but not excessive, appetite; isn’t losing weight or acting lethargic; doesn’t have diarrhea; and that parasites have been ruled out. If any of these symptoms are present, or if he’s vomiting green or orange liquid (bile), a medical problem is likely and should be investigated.
The two most common scenarios in which well cats vomit are (1) from eating too much or too fast, which results in vomiting undigested food very soon after eating, and (2) hairballs, which usually cause vomiting of the hairball itself. Hairballs have no sure-fire remedy, but the most popular thing to try is a hairball lubricant (make sure you give this on an empty stomach, not with food); also frequent combing, brushing, or even a "lion clip" (for a long-haired cat) will be helpful. Any hair you can remove is hair that your cat will not end up swallowing. There is also a new hairball formula cat food on the marketthat may help. Ask your veterinarian about this.
As for eating too much or too fast, this problem is usually worse in cases where cats have their food taken away and are only permitted to eat at certain times of the day, causing them to gorge when food is available. Trials of different brands of food may help. Anything else you can do (portioning the food out gradually, for example) to encourage eating smaller amounts frequently might also be helpful. If the vomiting is daily, you might want to try medication. However, most people don’t want to medicate their cats daily if vomiting only occurs once a week or less.
If these ideas don’t help you, the only way to get a certain answer as far as any medical cause, such as inflammatory bowel disease, would be to have biopsies of the stomach and intestinal tract done. Your veterinarian can tell you more about this.