My son started at 4. I noticed it after a tragic death in our family. He got speech help ( IEP) until 2nd grade. It pretty much went away until middle school. I wonder if maybe hormones played a role. He got an iep for speech help again, He’s now in 9th and is “ graduating “ out of speech. He’s done so well. They will continue to keep a 504 though for him. For your child, I would definitely get speech therapy if the stutter continues. It really made a world of difference.