Well, I've been testing this since I, too, occasionally get a mysterious 'ding' after a first start.
I've used the truck four times without having my cellphone with me and it does not ding. When I've put the cellphone back in my pocket and start the truck, it dings. Of course, there could be other reasons as well. Someone mentioned a 'Favorite' music detected on Sirius, and I believe that is true.
Regards,
Dusty
2019 Ram 1500 Billet Silver Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 3 June 2018. Now at 81880 miles