Hi! I also was diagnosed with POTS and had these “nocturnal panic attacks” for a span of about two months before diagnosis. I had the tilt table test done which was positive for POTS and once my cardiologist started me on a beta blocker (metoprolol) the late night attacks started becoming less and less frequent and now I haven’t had one in about a month! From my understanding, a beta blocker is usually the first form a treatment for POTS, maybe you should ask your doctor about it!