Peugeot 206 warning sounds when leaving car

hi.
This morning i had a strange problem.
1st thing car started no problem drove approx 3 miles to supermarket. after shopping car once again fired up 1st time and i drove about 200 meters to the petrol station. This is where things started to go wrong as i left the car i got the warning noise as if i had either left my lights on or keys in ignition (i had done neither).i Locked up using key fob and filled up with fuel. on returning to my can as soon as i put the key in the ignition the hazrd lights came on and the car would not start, the battery was fine it just would not fire up. I tried this for 15 mins.i pushed the car away from the pumps and left it there and was waiting for my friend who knows abit about cars. after about 20 mins i tried it again and The car started 1st time. i drove to work at lunch time i tried the car again and started 1st time. Any suggestions would be greatly apprciated, thanks