heart is pounding fast

If one runs up a hill it is normal to feel one's heart pounding. A heart rate normally increases with exercise, stress, going to higher altitude, etc. If one's heart rate is fast at rest, then it becomes necessary to look for a cause. For example, increased thyroid gland activity can increase the resting heart rate.
The question doesn't state how fast the heart is going, when it occurs, etc. It is easy to count a heart rate - count the number of beats in one minute. If the heart rate is constantly increased then the questionnaire sender should see a physician.
Please be aware that I am unable to diagnose medical conditions online.