Check your connections to the cam sensor (PCM) or crankshaft sensor. You should be getting a check engine light with it. On my old van, every now and then I get the same symptoms. I just get out and squeeze the connections together and it starts right up. Also, one or both of those sensors may be going bad, so replacing them may solve your problem. If you are not getting a check engine light, your problem may be a blocked fuel filter or a fuel pump going bad.