[feeling]

I have the same issues with my F10 2015 535D Pro Nav + Spotify. Sometimes it loads the BMW Apps properly and gives me the full Spotify interface which allows searching + listing of new music in sections, adding as a fave etc, compared to when it doesn't load the BMW Apps properly and just gives me "USB Spotify" with skip and backward tracks.

I have found 7/10 times it just doesn't work, but to get around it there are 2 things you can do.

1) Unlock car, plug phone into USB connection, press the ignition to boot the electronics, give it a few seconds, foot on brake and start the engine. This method usually gives me the BMW Apps Spotify screen.

2) If on the go and you've already plugged it in, once at a set of lights, turn off the car fully, then repeat the above, press the ignition to boot the electronics, give it a few seconds, foot on brake and start the engine.

I have found it to be a NBT (BMW issue) than iPhone as I had a 2016 BMW M135i previous with Pro Nav which was the EVO (NBT2) unit which loaded the BMW Apps first time every time, it was bliss.