Repetitions of classical stuttering involve a sound, syllable, or single-syllable word being repeated several times until the intended sound is produced. However, you've described whole-word repetitions in your post. I'm a layman, but what you're describing sounds like a "typical disfluency" rather than stuttering; typical disfluences involve "multisyllabic whole-word repetitions" rather than the single-syllable problems of childhood-onset stuttering. You can read more [here](https://www.asha.org/Practice-Portal/Clinical-Topics/Childhood-Fluency-Disorders/Characteristics-of-Typical-Disfluency-and-Stuttering/) and [here](http://www.stutteringsource.com/blog/is-my-child-stuttering-typical-disfluencies-versus-childhood-onset-stuttering#.XL9C0ZhKiUk). If the behavior continues past age 5, you may want to bring him to a speech-language pathologist (SLP). If you want to be extra safe and you have no money issues, you can bring him an SLP right now to verify that it's not stuttering.