My wifes nissan sentra wouldnt start a few days ago at the grocery store. I figured the most obvious thing: the starter. We pushed it off to the side of the parking lot, came back the next day, and it started right up. We took it home, figuring that she probly hit the gas accidently and flooded it. Now that its home it won't start again. Is there any way i can get it to start, just so i can take it to the shop. We have free towing on our insurance but its a pay now get a refund later type deal. A little help please!

Does it crank but not fire, or not even crank? More info please...

Sometimes its cuz the battery gets too hot. If your starting it in the middle of the afternoon it may not be able to crank because the battery is hot and it cant produce the correct amps. My old mustang use to have this problem becuase it had a really small battery for a large motor. If you cant fire it up in the morning, then replace the battery if it hasnt been done before.

It doesn't crank and its battery is a year old, and it is the right battery for the car.

Standard or automatic?
If standard - there's a clutch pedal posistion switch that won't let you start the car without the clutch being depressed. If auto there's a switch in or on the tranny that won't let you start without the car being in park - or yet another switch that won't let you start without the brake being depressed.
If the car is starting normally when it does start - and not cranking at all when it doesn't, I'd start with checking these switches.
If the battery is holding a charge and the alternator is working properly (lights aren't brightening or dimming when running) I suppose it could be a starter problem - but those don't tend to go away, (except when you need to tap on the starter solenoid to make it work <g>). If it was just the starter I might expect a few more symptoms too - clicking, or a "whiz" when the starter spins but the solenoid doesn't engage.
I suppose it could even be the ignition switch - but start with those first switches I mentioned - that would be the simplest problem and the simplest fix.

Sounds like it could be the alternator. Probably the Alt is bearly charging ur battery and if you let it sit for a while you can start it only to have the battery drain and causes you to stall out even while driving.