I too started having this ETC warning yesterday. 2018 Stelvio QV @ 13,500 miles. Looks to be the original Varta battery. Hooked up a multimeter to it and I'm getting ~12.54 volts with the car off after warming up the battery with the headlights. Seems a bit low, but then I realized - I was cleaning my seats this weekend, leaving the doors open and stereo playing for maybe 30 minutes? It was long enough for the car to shut itself off. So that battery drain is likely what caused it for me. The ETC warning and check engine light have both cleared as of today.