Intermittant check engine light?
 

My engine light comes on, and then will go off after a day or two. I suspect the gas cap could be the cause. Although the cap is only a year old.
Is there a better aftermarket cap for a W210?
Am I correct to assume that the sporadic operation of the light is most likely caused by a slight leak in the cap seal?
The car is a 97 E420.

No, that is incorrect. The chances that the light is due to an evaporative leak are about 1 in 100. The chances that your evaporative leak is the cap are about 1 in 20 maybe better.

There has to be at least a hundred different fault codes that will turn on the light. Each code has numerous logical possible causes and thousands of illogical causes.

To get the code read I hear Auto Zone will pull OBDII codes for free.

I have the same M119 4.2L engine in 1999 S420. Once I had my check engine light go off, they found that the ignition coil and spark plug on cylinder 8 were inop. If I were you, I would run to a mechanic. If your maf sensor is broken and you leave it alone unfixed you will destroy the cats, o2 sensor and eventually motor. Check Engine light is once there is two occurences of the problem. Do yourself a favor and go to a mechanic.