You could have a problem with your ignition, or your battery or it could be the anti-theft system that is causing your car not to start. I would start with the most simple thing and work my way from there i. e. your battery. Then i would start with your ignition system and so on and so forth.
Beginning issues could be battery, starter, solonoid. Then check cables and plugs and terminal connections. Check fuel and fuel flow out of lines. Clean carberatur. Check engine afterwards.
