Apple Watch Series 4 Heart Rate Spikes

I got my watch in Nov 2018. From the beginning the heart rate is always initially wrong, saying 150 then settling down to a more reasonable 74 bpm. Like right when I get up it says 150 and sets that as the highest rate and then settles down to 74. I will wear my twenty dollar finger monitor to check against the watch and it and it always says just 74.

Sometimes while driving or riding on the bus it spikes to 210 or 250 bpm, which is a ridiculous and impossible heart rate for me, especially while sitting on a bus.

My normal resting is 54 and average walking is 85. I have a few monitors and check against them regularly.

My question is, does the heart rate pick up on bumpy cars/busses? Seems like it should not be sensing things like that. Also, what is Apple doing to prevent these spikes?