Corsa D 1.4L petrol auto
I first felt a slight engine "judder" when idling in traffic on a hot day with the air-con on. I then noticed a slight wobble on the rev counter, it idles around 750, and the judder maybe causes a +/-75 wobble.
Opening the bonnet, on a separate occasion, this judder sounds like a "click" which causes the long thin pipe (not a mechanic) to judder. Video below.