Is an occasional fluttering feeling in chest during exercise common in otherwise healthy population?

Maybe. If you mean you can feel your heart beat fast after exercise, you may just be out of shape like me and that may be normal. If you really mean fluttering, ie an irregular heart beat you may have atrial flutter or atrial fibrillation, which requires treatment. You should see a doctor. He may want to put a monitor on you to see what your heart beat looks like on an EKG when you have the symptom.