In such situations just skip the first letter of the word, and trust me it works like magic - if you stutter saying Simon s-s-s-s-imon, or even block at S and unable to finish the word, just utter imon. And it does work brilliantly in both situations - one in when you stumble on repeating S, but then just purposefully stop trying to complete the word, and rather just say the ending of it. Which would eventually make sense to the listener. But it also does work when anticipating the stuttering, and even prior it saying the word which you believe is likely to be stutter, then just say 'imon', and after saying this outloud u are able to freely finish SIMON. Works with any word, and any letter.