Periodically I Have Rapid Palpitations (primarily When Exercising, Including Fast

Periodically I have rapid palpitations (primarily when exercising, including fast walking) on the right side of my neck--I assume this is carotid artery. My breathing is effected (labored) and I start to feel bad. I stop the exercising and stop to sit down and rest. I can feel the rapid palpitations when I touch the area in my neck--next to windpipe (i assume). What can cause this to happen? What do I need to do about it?