1996 Mercedes Benz S500

This could be several different things. If the vehicle is cranking but won't strat you may have a failed camshaft or crankshaft position sensor. Also you could have a fuel pump that is beginning to go out. Do you notice anything when you are driving? Hick ups, hesitation, low top speed, poor fuel mileage, rough idle, etc?

No, no hick ups, hesitation or anything like that. Sometimes the car starts right up, sometimes, it doesn't. Some days we can drive the car all day making numerous stops, and everytime we get back in the car and start it up, it starts. Then, inexplicably, we can get back into the car after leaving it sitting for about 15 mins to an hour, get back in ---- and nothing happens - no clicking, no attempting of the enging to turn over, and all of the lights come on the dashboard when the car is in the on position where the engine should be turning over.

Then after about 10 mins to an hour of trying, the car will just as inexplicably start right up like nothing happened.

And this doesn't happen every day or every time, just when it seems like the car has a mind of its own and doesn't want to start up.

My wife thinks that there may be a problem with the alarm and that it may be causing the car to not turn on.

If you have any suggestions, they would be greatly appreciated.

It could be an issue with the alarm but I would also suggest considering the ignition switch starting to go out. As the contacts in the switch start to go you can get these intermittent start issues with no crank. Also keep in mind if you hear a click when you attempt to start the vehicle then the starter may be your issue. If you have no click or sounds associated with the no start I would definaely recommend having the gnition switch tested.