I have a 2015 Golf 2.0 TDI that has done 35,000 miles and been serviced by Volkswagen since new. I've owned the car for 13 months. I've noticed the battery is losing its charge. It is normally driven on short journeys by my wife. However, for the past four weeks, it gets used twice a week because my wife is self-isolating. Any ideas why it's losing charge? My thoughts are power mirrors and stop-start have taken their toll, or alternator.