Yes, that's one of the main causes of anxiety. I'm anxious cause i want to speak fluently and say what i want to say nicely, and i'm afraid of possible blocks. It's a mind-block that it's pretty hard to overcome, most of the times its better to just go, don't care, and just say what you want (it's not easy at all though). For example, i used to never buy bread at the bakery stall at the supermarket ( i always bought the pre-packed one) because i was too afraid of stuttering when asking for it. I did it a couple of times without problems and now i just do it without thinking about it.