I actually have. One of my main anxiety symptoms is nausea/vomiting, and I've had those for no physical reason when I've either seemed relaxed or even excited. Although this is normally in situations where I might have expected to be anxious, but had managed not to be. I'd always thought of it as my subconscious being very anxious even though I'm consciously fine, although I don't know if that stands up under scrutiny by a professional just yet.