Did you ever notice that some stuttering is intentional? You might even do it yourself to emphasize a point, allow the listener time to think, or repeat a syllable because someone just coughed and you may not have been heard at least those are my theories. I think I catch myself doing it occasionally. It could just be learned from hearing others though.
“Sometimes a slight and not unpleasing stammer or impediment has been of some assistance in securing the attention of the audience ”
– Winston Churchill