What Causes Muscular Spasms Below The Breastbone?

I've been having (I think) muscle spasms for the past few days. They are located right below my breastbone, near the top of my stomach/right around or under the solar plexus.. These spasms don't cause any pain, and only last for a few seconds at a time. I have around a dozen or more of these throughout the day.

They're kind of creepy, as I can actually see the spasm "suck in" the area affected, and release as it's happening.

One thing to note is that I was in a car accident (rear-ended) a couple weeks ago, and it really messed up my back and neck more than they were before. The CT scan and x-rays came back OK, but I'm having a MRI on Tuesday.

I called my doc who was on call for the weekend, and he had no idea what was going on with these symptoms, and told me to check in with my GI doctor on Monday....but I'd just like to have an idea of what's happening; in the meantime, since they're more annoying than they are a problem.