Noma
You may be experiencing PVC's - premature ventricular contractions. Check out some web pages by that subject to see if that is your problem. You may be under stress or you changed some of your meds or supplements or certain foods such as caffiene may cause PVC's. Most PVC's are harmless according to "experts," but it may be worth checking with a doctor--there's only one of you. But you may try eliminating new additions to your diet/supplements to check this. It may take several weeks to notice the difference. If it's stress, you need to eliminate the stress.