We all have a certain rhythm when we write. Some people write fast, others slowly. (Just like with speech) But sometimes I also get stuck when it comes to writting specific letters or numbers. For me, those are: "s", "3", "5", "8" and "r". My brain just stops working, I lose my "writting fluency" and I have to focus when writting them. I think it's because of the curvatures and stuff... I think OP's just trying to make a comparison with stuttering verbally and trying to find a link between the two!