No, it's not. Have it fixed before warranty is up.
Though your description of flooring it (leg tightened and straightened, body pressed agains seat, pushing with all might) is sometimes how I realize I am upon flooring it! And my body instinctively flows (moves forward, then back) with the motion of flooring it! I can hear the CLICK Of kickdown very loudly as I push it so hard. I need to be more gently for fear that I will break it. Oh boy... me without kickdown, I would die!!
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)