So, I just kept playing it off and ignoring but I'm just too annoyed at this now. Anytime I open apps or the phone seemingly is loading something up or in the background, it makes my Garmin watch repeatedly disconnect and re-connect from Bluetooth. It is extremely annoying because it vibrated my wrist each time and it happens throughout the day, also killing the battery life.
It was perfectly fine on the same exact phone until I updated to recent GOS updates. Have tested the watch on another Pixel (same model but previous GOS version) and it doesn't happen at all. Again, it worked fine untiles a recent GOS update. Please fix or give info on this.