text: why does my heart start racing for no apparent reason? i am pregnant and 23 years old. one of the times it happened i was sitting in my car. i suddenly felt my heart start racing at 115 beats per min. i had no change in activity is this normal in prenancy? go to see your doctor as soon as possible it may be several things from panic attacks to a irregular heart beat. it is better to be informed so don't get scared and not go see a doctor.