Sounds like your TPMS sensors in your wheels have reached thier service life... given your model year listed (2004) - and if the sensors have not been previously replaced, the batteries are dead/dying.
I picked up my 04 in January this year and had the same issue, two of my TMPS sensors had completely dead batteries, the other two had very low voltage - i.e. almost dead. Service life according to MBZ for these sensors is about 4-5 years, so your well beyond that for original sensors.
If your sensors are still sending signal any Discount Tire or NTW/NTB can check to see if the sensors are working (your systems has the 315MHz BTW, NOT the 433MHz) So they can pull thier handheld scanner out to see at each wheel if the sensor is sending signal.
Also, untill the system is functional again, you will have to deal with pressing reset to get the error message to go away. It happens at start-up, and then about 10 minutes later - but after the 2nd notification (and your press reset again) the error message will not return until you shut down and restart your car, so for longer drives it wont annoy you multiple times at least.
Most tire shops can get you the Beru aftermarket replacement TPMS's (~$120 each), unless you just WANT to spend ~$300 each for the MB ones at the dealer.... either way Beru makes both.
I waited until I needed/wanted new tires and got all new sensors and tires installed at once, I did not mind pressing reset for a few weeks, but yeah... it can get annoying.