That's to wake the hamster that runs on a wheel that produces the electric charge needed to start the car.
Seriously though, no, I can't recall hearing a knocking coming from behind the dash when I start the car. Just the usually. Fuel pump turning on, radio coming on, then starter turning over when the ignition is keyed. Is your a/c on everytime you start the car? If so, try starting it with it off.
Sent from the Death Star.
2012 Kona Blue 3.7L V6:
Borla LT headers, O/R h-pipe, Borla S-types, 3.73 gears,
Steeda adjustable UCA w/ mount, BMR LCAs, Airaid CAI,
LCA Relocation brackets, AE driveshaft, GT 80mm TB,
Black 18x9/10 2010 GT500 Wheels w/ Nitto NT555s,
Eibach Sportline Springs/shocks & Koni STR.T Struts