Impala will not start - 2002 Ford Explorer Sport Trac

Ok so my 2001 impala started yesterday but this morning i turned to key over nothing came on the car woundnt even crank or start and before i started it yesterday it cranked over then when i let go of the key it started all by its self i need to know a for sure answer please

Car won't start?
Try this:

Make sure the positive cable, makes a good connection at the battery and at the starter. Make sure the negative cable makes a good ground connection at the battery and (preferably) at the engine.

• Check the battery the simple way, like this:

Turn on the headlights, then try to start the car.If the headlights do not dim or go out, then the battery is likely ok.

• Check the starter and solenoid:

If the wiring looks ok, then look at the starter solenoid for a good connection, and proper voltage at the starter(10 volts minimum while cranking).
If the starter spins and no crank, the problem is most likely the Solenoid's bendix gear is stuck.
Have someone hit (not too hard) the starter while you try to start the car. This usually works by dislodging a stuck bendix gear.

• Make a simple test of the alternator:

If you can, somehow get the engine running, measure the voltage at the battery. It should be at least 13.6 volts to properly charge the battery.