[1BADRS]

I have a very difficult problem. it is difficult because it is intermitting, only does it once in a while, but getting more frequent. sometimes when i go to start my car, the engine turns over but it wont start. i can hear the fuel pump come on and i smell gas by my engine so it gets fuel. when i have it towed somewhere it starts up immediately when it gets there. very annoying, can someone help me out? the towing seems to jar something to where it cranks when it arrives, whats going on!!