I started my car up last Sunday evening in order to reposition it on the driveway for an easy exit for the VW collection service guy. I was surprised by the engine noise that greeted me as I had not heard this before in two years of ownership. It was a drone or gruff sound/heavy sound but diminished after a minute or so. The car was serviced on Monday as arranged but did not mention this one-off thing. Since then, during the very hot weather the starts on one or two occasions have sounded a bit off but could be something allied to starting in hot conditions.
It has not occurred today (much cooler and raining) and so will see how this goes.