Knock in the rear and vibrate the door panel

Hello.

had already the next phenomena on the A8 4.2 TDI....
1.) When I stand with my fat and it runs periodically I have a knocking noise knocks about 30s long, then silence about 15s. Then knock again.

2.) My door panel back right vibrates. Got Bang and Olufsen and electric side blinds. Where are the screws? How can I get it?

Greetings Timo