Strange noise coming from the middle of the car? Help?

[Bigal1980]

Hi

i am new to the site I apologise if there is already a thread for this but I have owned a A8 for a few years now and I love the car. Recently I’ve had issues with it. Wheel bearings etc but all of this was resolved. I got the car back and when I am driving it there is a slight vibration in the footwell? Something doesn’t feel right with the car at all. I thought it was just me looking out for problems but my son in law drive the car last night and agreed there isn’t something right, online it says bearings near the gearbox etc I just don’t know where to start. I took it for a gearbox specialist and they said the gearbox is fine, full diagnostic on the car and again fine? Can anyone help and point me in the right direction please 

thank you