Sometimes when your calcium/magnesium ratio is off, you can get twitching.

I get one in my diaphram that feels like a fish flopping in my chest.

If you are low in calcium intake, or very low in magnesium, the muscles do a dance of sorts. So you could try to balance that out.

The Calcium channel antagonists used for blood pressure can make this worse, as the calcium metabolism gets screwed up a bit.

I have a magnesium thread on the Vitamin forum, with food suggestions and the best way to take supplements. Check it out...sometimes it is a simple thing to correct.