Hello. I had this too about 5 or 6 years ago and it worried me terribly. It was more.or less constant and I thought something terrible was going to happen. It got so bad that I took myself to A&E on New Year's Day! They did heart trace BP and bloods and everything came back fine. I went to the doctor whist waiting for a hospital appointment for a more thorough heart check who prescribed Propanalol and they stopped.... immediately almost. The heart check up came back fine. So I put it down to stress anxiety (even though at that time I didn't feel outwardly stressed) or, now, menopause.