If your dog is acting like it is going to throw up soon, the possible reasons are • It has ingested something that has resulted in an upset stomach. • It has eaten its meal too quickly and has probably overeaten. • It is already suffering from some ailment which is making it nauseous. • It is on some medicine (probably due to issues like ear infections), which is making it uncomfortable, and it wants to throw up. • There is some foreign material lodged in its throat, and it is trying to throw that out.