I have a 2018 580-2 and have been experiencing this for more than a year, through intermittently. It affects only Satellite Radio; FM and AM work fine. It's very annoying, and turning the car on and off doesn't fix it. But if I leave the car for 10-20 minutes and come back, it works fine. I've taken it 3 times to the dealer; they've even replaced the MMI unit with a supposedly "redesigned" one (had to wait 3 months for it), and the problem is still there. When this happens, switch to FM, raise or lower the volume, then switch back to Satellite Radio. I know, it's a pain, but I gave up on the dealer. The car is due for its second annual service next month, and I'm taking it to another dealer. I'll see if they come up with a solution (or the cause of the problem!).
It's a good thing that the sound of the engine, especially with the top down is the best audio one can have. Who needs Satellite Radio?! :-)