According to an article on ScienceDaily, moving your hands and making gestures while speaking can help you to access your memory and language. A study at the University of Alberta found that bilingual children who were observed telling the same story in two different languages tended to use gestures more in their stronger language. The researchers believe that moving your hands helps you to recall parts of the story.
The researchers initially thought that the gestures made while speaking were used to convey information. They now think that the gestures are related to memory. So if you find that the words just are flowing, trying moving your hands. It might just help.