I stutter on certain letters ( like h, k, f), when I was little I used to go to a speech therapist. He tried to help me for like 3-4 years, but it didn't really help. Usually it is very hard to start speaking, but I don't really stutter once I start to focus what I am going to say and not how am I going to say it. My personal experience is, that people feel very weird around people who stutter. That's why I don't really have a big friend group, only a few (like 3-4) close friends.