Heart app on Apple Watch 5

I have always enjoyed using my iwatch 5 to track number of hours I sleep. Recently, my watch has been waking me up 2 or 3 times a night to alert for heart rate spikes. To check this out, I wore a heart monitor for several days and had an echogram performed by a cardiologist, both of which resulted in normal readings. This has been very annoying as I now cannot wear my watch when I’m sleeping, which is the only time this occurs. Interestingly, this does not happen during the day.