I'm not on HRT, but believe I'm in perimenopause.
I started getting palpitations back in October (or, at least, that was when I first started to notice them properly) but my GP had previously mentioned I was tachycardic in June during a routine examination.
Mine most frequently happen at night, but some days, they carry on for several hours in the morning too. I have just started to keep a diary of symptoms to see if there is a pattern - they completely disappeared at the end of last week and over the weekend, when my period arrived, and then returned once it had stopped.