1998 Dodge Intrepid Wont start

I cannot get my 1998 Dodge Intrepid to start. I turn the key and all my dashboard lights come on but it doesnt crank or make a sound...nothing happens. I got it out of the shop 2 months ago and they replaced my timing belt and my water pump. Before that my fuel pump was replaced. It ran for a month and then one day I started it and it died and hasnt started since. Another thing is ever since I bought it used it stalls out while driving.It doesnt matter if I'm going 15 or 65 mph. I could restart it by putting it in neutral and turning the key. I've had the battery, alternator,starter and relays checked....all of them still good. I replaced the ignition switch because of a crack on it.....still nothing. And had my key and lock and tumbler checked....those are good.
I've been told to check for a bad sensor , but i dont know which one or where. Please help!!