Intermittent Starting Problem

[Captainmagenta]

Hi team hoping you can help with a problem on my A3 convertible.  Sometimes when I turn the key to start the car nothing happens. The dashboard lights come on as expected but there is no sound from the starter. I can turn off and on again - still nothing or might start. Third time it starts as normal .  Then days go by with no starting problems at all.    
Battery was new last year and checks out as fine.   Any ideas what might be going on?

thanks

[Steve Q]

I'd recommend a diagnostic check to see if any fault codes flag up. Could be a crank sensor. 

Is there any red light on the dash which could indicate an issue with the imobiliser? 

[Captainmagenta]

Thanks Steve. I should have said no fault codes show up on OBD. 
I wondered about the immobiliser but no red light on the dash.