They started for me about 6-8 months ago. They are terrifying. Initially they were very severe, particularly at night. Early on it felt like my heart was trying to leave my chest, and I was sure I was dying. I've had a stress echo and the cardiologist assures me by heart looks just fine. They are no longer as 'forceful' but they're there a lot...more like flutters that I get quite regularly. I can go through days and days of none, but they always come back. Almost assuredly hormonal for me. Often precede hot flashes, episodes of anxiety etc. They're all linked together. Fun times.
Tara