high-pitch dash buzz--Thanks for the help on that!
 

My 98 ML320 is making a sound when I start the car, first thing in the morning (or when sitting for any long period of time). I have been told that it is the blower motor for the fuse box. Does anyone else have experience with this type of sound? Also, is there a fix to this, or does the blower motor have to be replaced? Thanks!

Yup, blower motor. Ours actually sounded like a buzzer, only a little sickly sounding. It was replaced under warranty, so I don't have any details on how much it costs.

It could be the water pump too, mine sounded like that when first started the car and it does not do that every time (a loud chirping sound identical to the bad fuse blower motor). Locate the source of sound first. If it's near the upper radiator (as opposed to near the fuse box), your water pump is going bad. Replace it before it grinds out your timing cover.

I had that problem too. It would just happen when I was driving...all of a sudden it would sound like some type of alarm was going off. Then, my entire electrical system went out one day (wierdest thing ever...you would shut off the key, take it out, and the car would keep running, or, turn it off, but every light in the car would turn on). MB replaced my whole fuse block and assorted associated items, and the noise has never come back. And, turning off the key shuts the car off! So, it sounds like fixing the fuse panel fixed the problem (they may have changed that blower as well, can't remember as it was a covered reapair so I was not too involved in it) so that very well could have been associated with the blower in that area.

I had the same problem too. Took the e-box motor out and tried to lube it with engine oil, that didn't help at all. Asked the dealership to replace it when the truck was at its last A service, the service advisor said that's pretty common for ML and replaced it without any issues.

If your truck is out of warranty, you can replace it yourself very easily.