if i have bad spark plugs can Mercedes onboard computer notify me?
 

if i have bad spark plugs can Mercedes onboard computer notify me? Should i change those or not? Sometimes when i drive it feels heavy sometimes it goes and accelerates fast and smoothly. Maybe its due to hot weather and ac compressor or im just going crazy.

If it gets so bad or stops working completely yes you will get a CEL and it will run like crap. But if it just gets old and is not to that threshold yet then no it won't tell you anything. Best way is to follow guidelines which for a m112 I believe is 100,000 miles (that's when I did mine at least and new wires at 200,000 miles)
So how many miles and how old is your car?

The computer codes will show misfire if a plug is failing. It can be for a list of reasons.

I changed my plugs at 85,000 just to make sure they didn't seize in the head.

95k

What year is your car? I would probably just do it though if they are original from say 2003-4. Not to hard of a job with the right tools be carful with the wires as they can brake if pulled on you need either the special wrench or a pair of pliers that have a strange bend in them I got a nice set from harbor freight that worked great when I did mine. That said if you like to keep your car in top shape a new set of OES Bosch wires is under $100 on amazon which isn't bad at all.

Alright!