I just got mine yesterday, but I have not encountered that yet. I'm using Spotify Premium, and I used it in my Subaru (a bit glitchy at first, but I fully attribute that to the Subaru Head Unit) as well as using it as a controller for my laptop.
I know there was an option on my V20 where it would launch an app automatically when connected via Bluetooth, or headphones were plugged in, or WiFi was connected. I checked my settings on the Note8 but I have not been able to find that feature. I have a feeling that is what is happening. I'm not sure if that is an Android feature, or an LG feature though. Hopefully, that will help in some way.