This is a great question. In scholarly papers it is usually depicted as, “Y-y-y-you..” Are you the one writing? If so try not to lean into the part word or single sound repetitions. The single sound repetitions are very cliche in depicting stuttering in media both written and visual. There are so many more interesting ways to stutter. You can use blocks: “Whe- - -re is it?” Interjections: “I - um- um - go there” Phrase repetitions: “I go - I go to the mall.” Revision: “I ride my bi-bi- -scooter” Even use a combination! “W-w-w-where is my - is my - is my bi- - -scooter?”