Not necessarily. It depends on how he sounds and behaves when speaking.
Lots of young children stumble over their words as their language develops. Sometimes what they want to say exceeds their ability to actually say it, and they end up repeating their words while they try to work it all out.
This is normal and not a cause for concern. When this happens, make sure you don’t talk for your child or rush him to finish. Instead, slow down your own speech and the pace of the interaction with your child, and make sure to give him your undivided attention.
Rather than asking open-ended questions that require complex language to answer (for example, “What did you do on the playground?”), try simplifying the questions to reduce the language demand (“Did you play on the swings or the slide?”).
Stuttering will sound noticeably different than normal childhood disfluency. A child may repeat the first syllable of a word rather than the entire word, prolong the sound in a word, or move his mouth to say a sound but produce no sound for a few seconds. He may also avoid saying certain words or make unusual body or facial movements while attempting to speak. If you notice any of these signs, a prompt evaluation by a speech-language pathologist is recommended.