Vibration at idle?

Drove around in my a3 yesturday, I was parked up in an industrial estate using my phone with the engine running (in P, with handbrake on, s-tronic) and I noticed my car vibrating / shaking slightly every half a second or so. Like a petrol car does with a duff ICV except much more subtle and according to the tachometer the revs are constant 800rpm or so.

I have full audi warranty until December so I am wondering what this could be so they can fix it under warranty instead of me requiring to? It has no mods yet (due to warranty) and when warranty runs out I want to do downpipe+sport cat + remap.

I appear to have won the audi lottery when it comes to oil, only used 1L of oil in 6000 miles.

Car is a 2010 2.0T TFSI S-Tronic I can't remember the engine code but it is the phase 3 one. Engine looks like this I think it is CCZA?


Car itself

All the tdi's I have owned vibrate, that's just the diesel engine. On a petrol though...

I am wondering if it is the famous chain guide thingy, I started the car up yesturday cold start and it seemed to make a wierd grinding noise for about a second after start up, a bit like when you shake a box of spanners. Turned it off and back on again and it was fine. It is like 300miles away from 70k if that makes any difference?