I just purchased a 2000 S430. It has two problems which may or may not be related.
1. The SRS light comes on when starting and never goes out.
2. After driving the car a while the headlights begin to flash from dim to bright, randomly. I would guess bad battery, alternator, or ground.

Has anyone had any experience with either of these issues?

 

Unlikely linked issues but possible.

SRS needs to be scanned and reset by dealer. No alternative. They will advise what is wrong.
Both headlamps or just one? Xenon or Halogen?
If one likely the bulb especially Xenon.
If both then likely supply which could be linked to SRS. Need to check fuses and fusebox etc.
Stuart

 

Really?
What in the alternator could possibly cause the headlamps to TURN ON and alter brightness intermittently?
I agree the alternator COULD be linked to the SRS issue IF it was producing over voltage but I would have expected the Battery warning to have also been signalled.
Over voltageusually trips several circuits out.
I guess if the headlights were on AUTO over voltage could possible cause the dim/bright malfunction.

Anyway an alternator (or voltage regulator pack) is not a cheap item so I would still get the diagnostics scanned to determine what codes are stored before spending my money.

Although I'm surprised by your response I'm always willing to learn something new.
Have you actually had this exact problem yourself. It appears you also had flashing red warning
Stuart.