Alright, your seatbelt (probably drivers side) buckle has been damaged. When the SRS light comes on after starting the car, but goes out after a minute or 2, then the seat belt buckle is damaged and the SRS system cannot tell if the seatbelt is plugged in or not. Either something could be spilled in there, or it could be broken, or just worn. You need to replace the buckle, which comes with a wire, and 2 connectors. Once you replace the seatbelt, the light will still be on because it needs to be reset. I had to pay the $90 to take it to the dealer to reset it!! I hope I made that more clear this time.
Ok, to remove the casette holder...
On the console, where the shifter is, there is some plastic trim that surrounds the shift gate... pull this up and off, you might need a flathead, but be careful of the wood! Once you get this trim peice off (rectangular shaped with rounded edges), you will be able to pull up the console slightly from the front, by the ashtray. Pull it up just so it loosens up a bit. From there, pull the small storage pocket below the ash try firmly, and towards you. It should come out. Once you do so, you will see 2 screws, one on either side of the ash tray at the bottom. Be careful of these, because if you drop them, they're long gone! You might only need to loosen the screws on the ash tray a bit so that you can rotate it just enough to get the casette holder out.
GOod luck and if you have any other questions, just let me know!
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!)