Probably because he's eating too fast. My cat used to do the same thing. She'd wolf her food down and barf it right back up after only a minute or less. My vet suggested that she's probably eating too fast and swallowing a lot of air, and vomiting as a result. She suggested feeding little bits at a time. Try putting his food down, and taking it away after he eats a few bites, give it a few moments, and give it back to him. Repeat until he's done. Solved my problem.
Could be a couple of different things, he could have hair balls, they tend to make cats throw up. But it could also be just the nerves, don't feed the cat soft food all the time, if you're doing this, they need the hard food for the health of their teeth.
Keep a larger bowl of food out for him, this way it doesn't get empty as fast, and pretty soon, he might be comfortable with first seeing that he isn't out of food, and knowing that it's not going to run out, he might slow down on his eating.
Which in turn, might help to get him to quit vomiting, this would take a while to get him use to, because it's a learning process, and it requires time.
If it persists after a couple of weeks, then I would consider taking him to the vet, because it could be something else underlying the condition.
In the meantime, this gives you some time to save a little money for the vet bill, if that is going to pose a problem for you.
I almost forgot, leave the food out for him all the time, this way he knows it isn't going to go anywhere. Hope this helps, good luck.
I have a cat who does the same thing quite often.Usually because he has already eaten and then can`t help himself from hunting ( that`s what cats do after all !) and then after he has caught and killed a vole will eat all but the back legs, intestines and tail and then throw up.He doesn`t care either!Nothing to worry about, but he should be wormed every three months.
