Google Play Music and Bluetooth

On my old phone, an LG G4 with 5.1, when I started my car and turned on my stereo, Google Play Music would automatically run and start playing music. On my new phone, a Nexus 5X with 6.0, I can't get that to work. It will work if it's the last media app that I had open, say if I was playing music earlier in the day, but if I use any other media app throughout the day or reboot my phone and then do it, it doesn't play anything unless I manually start the app again and hit play.

I'm not sure if this is a phone model thing or an Android version thing. I did some searching and I can find about a hundred examples of people wanting this to NOT happen, but I guess I'm the odd one out. Any help would be appreciated.

LG has a tool that works in vehicles specifically (it's pretty much automagic once the location is known to the device) so that could have something to do with it, think it's the LG Car Mode thing (I'm using a G2 nowadays which doesn't have it in the custom ROM I'm using, but then again I don't own a car so I'd disable it anyway).

This works exactly like this on my Motorola Droid Turbo and my last galaxy s5

Hm, maybe just an LG thing that made it work before, then.

Anyways, I installed an app called Bluetooth Autoplay and that seems to do the trick. I can tell it to open Google Play Music and hit Play whenever it connects to my car via Bluetooth.

I had the same issue when running the factory ROM on both my Droid MAXX and Nexus 6. Switching to CM made it go away. This was with a Sony HU. Didn't have this problem when I rented a Ford Focus or Mazda3 so it could be your receiver too.