SRS light on for a minute after start-up usually indicates that one of the seat belt buckles is faulty. ETR is disactivated, and the airbags will deploy in minor accidents (whereas, ETR would have activated... but the SRS system doesn't know if the belt is buckled or not).

SRS constant on could be a number of things. My dealer charged me $90 (!!!) to read and clear the SRS code (I replaced the buckle myself).

Good luck,

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
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!)