I recently bought a used Mazda 6. In the last two weeks I have had several instances where I put the key in to start the car and the ignition won't unlock to turn the key. When I get out and lock and unlock the car several times it will finally unlock and start. I worry that eventually it will cease to turn over at all. I know that it is not normal for this to happen. What I don't know is what is causing it. Is it something to do with the key fob or anti theft system? I have no trouble activating the key fob so it's not an issue with the key fob battery being low or dead.