Apple Watch series 10 random heart rate spikes at rest or sleeping

I’ve recently switched back to Apple Watch after having a Fitbit for a few years, I’ve got the series 10 GPS and had it a week now. On 2 seperate occasions my heart rate has spiked randomly and only for a few minutes then drops right back to my usual heart rate.

the first was while sitting and spiked to 173 and dropped back to 63bpm. Then another time while i was sleeping it spiked to 136bpm for again a few minutes then dropped to my normal rate! Should I be worried or should I return the watch? Never got this with my Fitbit . Now questioning to keep with Apple… I’m trying not to worry but I don’t have any other symptoms at all.