I am having trouble with my ignition and starter motor...

My car has been running fine for the past 2 - 3 months starting first go idiling o.k (only on cold mornings) but i have hit a wall in the past 3 weeks...

It first happened when i drove down to our ovals at skool, i parked the car turned it off FINE. 2 hrs later went to start it up and got a low 'whine' and then just died out, tried again nothing.. Took of -ve terminal cleaned dizzy cap, cheked coil, leads all fine then looked at starter motor and twas fine aswell..Cheked fuses none blown and jsut let it sit there for 1 min. Tried again and it started fine! quite werid
This happend to me about 1 week later, drove for a while stopped parked, turned off, BUT this instance it did start but it would jsut die on me if i didnt rev it and my battery lite was on even when i did rev it. went thru same process as b4 and it worked fine WEIRD!!!
Happend again 1 week later, wouldnt start unless i roll started it to get the start motor moving, drove it home left till next morning and then started first go!! WEIRDDDDDD!!!!

Has happened again today, started fine the smorning, everything fine sounding clean then when my dad came out it just died and i couldnt start it again, we roll started it and it went fine, parked turned off & wouldnt start....ARRG!!!!!

PLEASE could some one tell me what the hell is wrong with my Sunny wagon!! I have suspision it is a bad terminal in the switch FROM the starter to the battery, i know that the starta motor tis fine...
I have recantley just placed a Pioneer head unit and 4 speakers inthe wagon but it has never suffered from this problem until those incidents!!!

I need ASAP, it needs to be running!!!

Thanks tons
Cheers
Dave