ML320 - Intermittent 'whistling' noise on first startup of the day. The noise typically lasts from 5 to about 15 seconds and then disappears. Seems to be coming from behind the dash in the vicinity of the passenger-side SRS airbag.
Anyone experienced anything similar

Yep, on my 94 E320 but it continues for about 10 minutes. However, I can stop it by turning the engine off and back on after driving about 5 min. There is some info on the board about this.
regards,
Mark

Hi cgsmith10, it sounds like your module box blower motor needs to be replaced. Try this. Remove the fuse box cover first thing in the morning. Have a helper start the engine while you check inside the fuse box for the noise. I do a couple of them every week. Good luck.

This is exactly what my car has been doing. Thanks for the information!