2000 ML320 Check Engine Light

[BenzBob]

Lately my Check Engine light has been coming on while driving. After coming on it usually clears itself out after about two(2) days of driving. I have checked the gas cap and found the seal to be good, as it must, since the light has come on and also cleared itself out on the same tank of gas without ever touching the gas cap. Since the light usually comes on while driving at highway speeds (70 mph) I thought it might be the Mass Air Sensor that is getting weak and needs replacement, but the vehicle is running great and has shown no change in gas mileage. The vehicle has 42,000 miles on the odometer and I have not yet had a chance to take it to the dealer to get the codes pulled. Since it always resets itself (has done so three times so far) I am starting to think that the condition is intermittent and may not be easy to troubleshoot. Has anyone else experienced this intermittent CE light issue that always clears itself? Your thoughts would be appreciated especially if it is something I can address easily myself.