I get stuck only on the beginning letters or sounds of words. The letters change through time too. L, E, R, TH are some that consistently give me problems. Also it's not every time I say those sounds. Sometimes I can speak for 10 minutes fine and then I trip up for the next 5. I have a very minor stutter and when it becomes pronounced, I might stutter every 25-100 words. An example is the word Thank You which I often have trouble with. It's the motion of moving my tongue and mouth from the TH sound to moving my tongue and mouth to the A sound that my brain just can't comprehend so you I just make the TH sound for 3-5 seconds. I'll stop, take a deep breath then try again. Taking those sounds (mentally) slower also helps overcome the stutter word.