When you turn the key to start the car, does the starter actually spin the engine? Or is the starter spinning the engine, and it is not firing up (when you release the key). Or is nothing happening?

 

Suggest getting some help, opening the hood, and listen for noises from the starter when key is turned to Start. From your description, the solenoid contacts may not be making contact. They wear out and usually result in a sharp click when solenoid throws, but no starter action.

good luck

 

Never saw the tach move so I can assume the starter is not spinning.

Be sure the cables are clean and tight where they connect to the battery. Do you have a volt meter to take some readings at different places and under some condidtions?

 

A faulty alarm can cause strange problems with a car.

I would disconnect the battery, and clean all ends of both battery cables using a wire brush.

See if your alarm has some sort of reset on it.

 

Update:

Had to get the starter replaced.
$500 for the part, labor, and the tow.