If you have an older luxury car that still runs well, such as a Mercedes, you might have no plans to replace it yet. That's fine, but that doesn't mean you have to keep all of the outdated features. For example, if your car has a typical car alarm, the type that lets out a series of wails and sirens when it's been triggered, you can have a repair shop disable that and install a much better anti-theft system. Upgrading to a newer system will give you a better chance of stopping theft and not annoying your neighbors.
Why Disable the Old Alarm?
So many people have had car alarms over the past few decades -- and so many of those alarms have gone off at random times, usually in the middle of the night -- that no one really pays attention to them anymore. Your car alarm could be going off, and your neighbors would just assume that a cat jumped on the car. Even if you recognized your own car alarm, would you really want to meet face to face the people trying to steal it?
If no one's going to pay attention to the alarm, it's not going to stop thieves. You may as well save everyone's ears and have your mechanic disable the alarm.
That doesn't mean you have to go without protection for your car, though. Have your repair shop install a silent alarm, one that doesn't sound off audibly, but instead sends a message to your phone, for example. You have a chance to call police then, and if the system includes a tracker, you and the police can go find the car and possibly the people who took it.
Another option is an immobilizer. This requires a matching key -- there's a computer chip or similar feature in the key that unlocks the immobilizer -- and if there's no match, the car won't start. So if someone's trying to get the car started through hot-wiring, it won't work. Immobilizers won't stop thieves from taking valuables from the car, though.
Check out http://www.checkeredflagimports.biz and talk to your repair shop, especially if it specializes on working on Mercedes. The techs there can let you know what problems and benefits they've seen from silent alarms and immobilizers. But in the meantime, they can disable the old alarm and check your car over for other issues you might need to address.