Wrt the walking by the car part: If you are using an Android phone there's some setting buried deep in the developer menu where you can set the max number of bluetooth devices it should connect to down to one.
It makes it a little less shitty, so that when you're on your headset it doesn't switch to the kitchen bluetooth speaker (for example) just because someone turned it on and your phone is within range.
If you're not using a headset, the only option afaik is to turn off bluetooth.
But yeah, most UX sucks 🫏-balls