My phone (a Moto Z Play) has always connected to my Bluetooth headset automatically when I switch the headset on. Never had a problem or a hickup. Back in November, I bought a truck with a Bluetooth radio. After I connected the phone to the radio, it quit connecting automatically to the headset, and it also wouldn't connect automatically to the radio. I had to select what I wanted it to connect to each time. After a few weeks of that, it went back to working normally. I could switch the headset off when I got in the truck, and after I started the truck the phone would automatically connect to the radio. When I got out, I could switch the headset on and it would connect. Now it's gone back to making me select what to connect to. I haven't changed anything on the phone, the truck, or the headset. Phone hasn't updated firmware or anything like that.
What's going on with this thing? I sure wish this stuff would just work, I'm tired of having to 'tinker' all the time.