2004 C240 Alarm Issue
 

This has just come up. Every once in a while the "alarm" goes off for no apparent reason. I say "alarm" because it's not the full bore alarm but a sort of low pitched cycling noise, not very loud; it sounds like someone's alarm is going off a block away.

The lights don't flash, and it stops when I hit the door-open button. I get no "malfunction" light or indication on the dash, and the car drives without a problem. It has happened twice, in neither case with evidence of anything coming in contact.