There are lots of reasons for irregular heartbeat. From too much caffeine which causes stimulation to the heart muscle to perimenapause . In most cases it is harmless and requires no treatment but if syptoms persist ther may be an underlying and more serious problem which may be treated with beta blockers or defibleration. Always best to check with your Doctor
It depends on how long it lasts. If it happens intermittently, just one beat at a time, then you are likely having PVCs, or premature ventricular contractions. Basically, that just means that sometimes you have an extra heart beat that comes before the next normally scheduled one. More noticeable when you are resting than when active (because more time to occur between normal beats when the beats are more spread out). Nothing to worry about.
If it lasts for longer than a second (meaning many seconds to minutes to hours), then you may be having a sustained arrhythmia (or abnormal heart rhythm) that warrants investigation. Again, nothing to worry yourself sick over, but definitely work looking into, in case it needs treatment.
See your doctor. If the episodes occur daily, he/she can set you up with a Holter monitor. If they occur less than every other day, then you may need a longer assessment, like an Event monitor.
When we rush about, or are ill, feel stressed and frightened, the heart can pump harder to get the blood round our body.
You can feel the heart beat by pressing on certain arteries. Like on the wrist or the neck.
If you feel that your heart beat is not beating regularly or starts to beat very fast for no reason, it would be a good idea to see your doctor for a check up. ECG tests and referral to a cardiologist if the doctor feels it is required.
My daughter in law has a birth defect in her heart and that will start to beat extremely fast for no apparent reason. She is on medication from the cardiologist for this.