I am in my early 30s and I have had a stutter since childhood. It was pretty serious when I was younger, currently pretty manageable - many/most people I know don't know(or remember) that I stutter. As I get older it's become more of an internal battle. I am pretty good at hiding it.

If I am relaxed I can talk for long stretches without pauses. But occasionally I have to take a second or two before I can get a word out, this is especially disturbing during a dialogue with a person I don't know. It's even stranger when it happens in the middle of a sentence. I am sure I have left many people the impression that I don't know something extremely basic, or am mentally handicapped in some way. I usually make a thinking face and vocalize a "hmm..." if I feel a stutter coming up, it's better than staring the other person silently during my internal struggle.

I know a word is going to cause problems even before I try vocalizing it, my brain let's me know in advance, I can feel the word being broken...blocked...sharp. I often reorganize sentences to get around them. If I really need to use that specific word I may start talking about something else, while battling with the word in my head, usually I can insert it into an in-progress sentence, instead of starting a sentence with it.

I think I only stutter when the word begins with a strong letter, like k,t,p. I may also be subconsciously bending/smoothing the other letters without others/myself noticing, but getting a k,t,p - especially at the beginning of a sentence - out of my throat can be really challenging.

Collecting myself, changing my posture, looking elsewhere, coughing, etc. can ease the first vocals out. Slight coughs or throat clearings are especially good for masking the bent first letters. Too bad about coughing not being in vogue right now.

It will not happen during singing, only conversation, especially when I feel its a stressful situation - eg. even asking something trivial from the shop clerk. When I was younger there were many things I left un-bought because I couldn't vocalize them to the clerk. I don't remember myself ever stuttering on the phone - though I may misremember. Sometimes I don't remember when I last stuttered, though I might not register it as an event any more. It has not ruined any moments. I have probably organized my life to have less triggers to stutter.

Overall it's a pretty stupid thing and I would prefer not to have it.

EDIT: I only stutter in my native language, I don't stutter in the couple of other languages I know.