Hi there, I'm a speech-language pathologist who stutters. He may be going through a natural phase of typical developmental stuttering if these are light repetitions and no blocks. In 80% of cases, there is spontaneous recovery. I would keep an eye to see if his light repetitions develop more into severe blocks and also if you notice him becoming self-aware, frustrated, or avoiding speaking d/t stuttering. Also, one needs to consider if there is a history of stuttering, as well as whether there is a genetic component in about 50% of cases. The biggest piece of advice I can share is to praise his communication/what is being said rather than how he is saying it.