Possible wiring issues?

I have a 04 CLK 500, 130k. I've had it for a year now and everything has been great, until now.
It started with random warning messages for tail light being out. I changed the bulbs and the messages come back. Then the battery wouldn't hold a charge so I put in a new one, but that is not the problem. The SRS light is on now and I continue to get different messages from light being out to the display defective, SRS warning to the car just wont start. Sometimes the seat controls and steering wheel adjuster works and sometimes not.
Any ideas. Could it be wiring or a relay or even the alternator?



