I got this issue, and loads more with the infotainment system. After much nagging, 9 months of “It’s fixed so it must be your iPhone” from the service manager, they replaced the entire head unit free of charge. It is a common problem but Skoda don’t want to admit it. It happened on my wife’s Fabia and my son’s brand new Fabia. The service centre disconnected the DAB aerial and that fixed the issue in their cars. Mine has started doing it again but only when the temperature is hot, on cold days there isn’t an issue. I got some advice that the slider strip, for volume control, under the head unit has poor connectivity so when it gets hot it starts increasing volume as some of the connections expand in the heat. Apparently taking the strip out and cleaning with isopropyl alcohol resolves the issue. Another fix I have been recommended is to take out the fuse, fuse 30 is for the head unit controls, and simply use the volume button on the steering wheel to control volume - the touch screen works as normal. I’m going to try both this weekend.