Hopefully someone with technical expertise can advise me on a problem I have with my S60. I have a 7 months old S60 auto and twice there has been a problem that concerns me. Sitting in traffic in gear held by the footbrake when I transfer my foot from brake to accelerator there has been a bit of lag then an uncomfortable thump as it takes up power. This happened even when running in stop start traffic making the change to neutral not an option. It has only happened twice but as car is under warranty I would prefer to get this sorted if it is something that needs attention. Any idea what would cause this and what the repair would involve? Just to clarify I wasn't holding it in gear for any length of time, simply a few seconds.

Cheers

BL