Apple Watch Series 3 Heart Rate

Good evening Folks,

I bought the above roughly three weeks ago and have been using it every day since.

Now I wouldn't say I'm an overly healthy person, but I wouldn't say I'm totally out of shape.

I have a couple questions about the Heart Rate feature and if anyone else is experiencing the same problems.

When I check my heart rate for example for the first couple seconds it will show 95bpm, then all of a sudden down to 70bpm (which is what I would think my heart rate would be roughly about at the time of checking), does this problem happen with anyone else? I mean I've seen it go from 110bpm to 65bpm within seconds and it totally ruins my health app readings (obviously I can delete them, but you think it would wait to show an accurate reading).

Also I recently had a Fitbit and wore it for roughly a month which gave me a resting heart rate of approx 66bpm, however the Apple Watch is showing my average as 53bpm, I feel this is a fair difference?

Hopefully see your responses soon.

Thanks