I stutter and stammer and other times I will be able to talk as clear as a bell. It really annoys me when I have a block and it goes in fazes where it won't occur for months then all of a sudden for know reason at all I can't make a call without a lot of hard work.
Lots of pilots I fly with will be surprised because it can go for months before they hear me stuff up and are taken by surprise as I am.
I don't think we should worry about it,its rarely heard/noticed by others, its just we're sensative to it.
Good luck and SMOOTH SPEECH