I experience it as well, it is more evident after working out.

It may seem strange, but for me snacking half a cup of whole grain cereal, an apple etc seems to make it less pronounced. I guess it has to do that the blood goes to the stomach. Drinking unsweetend green tea also seems to help.

It may seem strange but since I added strength training to my routines the symptoms are little by little fading away.

Of course like others say tell your doctor etc.

In my case everything is good so far as I had a physical exam about a week ago. From an electrocardiogram, thyroid, testoterone, hemmatocrits, blood pressure level tests where done and everything came back fine. I follow a healthy diet, non-smoker, no alcohol, monitor my workouts with heart rate and I know it is not over-training etc. I say it just as reference... I am still trying to kick caffeine, maybe next year's resolution, lol.