I admit up front that I am no doctor, and my arrhythmia is AF, atrial fibrillation, about which I have learned much. Probably just enough to make me dangerous. 😀

SVT seems to run in couplets, triplets, and quadruplets...mostly, and then they go, but it depends on the type and on the patient. Palpitations is the word the doctors use to describe what patients tell them they feel. It isn't a diagnosis, just a symptom. And palpitations can be experienced with AF, SVT, and with PACs, (premature atrial contractions). In fact, since you seem to know you are NOT in tachyarrhythmia, your words being '...even when my heart rate is within normal range,' it is possible that you are getting some PACs....don't know if they showed up, but maybe they are doing that recently. The thing is that atrial tachyarrhythmia might not show all the time when the ventricles are not trying to keep up and just show normal rate. And some AF can be under 90 BPM, but it's still a wonky atrial rhythm that works against the rest of the heart.

Here is a very technical article that will explain a lot to you if you care to wade right up to your chin in it. 🙂
https://johnsonfrancis.org/professional/ecg-basics-a-brief-review/supraventricular-arrhythmia-part-1/