I know that feeling. When you feel incapable of speaking unless there's certain physical movements that accompany what you're saying. A lot of it is to do with discomfort and time constraints. When we feel we need to talk at a certain pace etc. I've found that taking a moment to breathe, then speaking on your out breath, can help a lot. It's something I do often - but should do it more often. Hope I've understood this correctly.