Won't start sometimes...

[Super Ace-K]

Recently in the S12, I turn the key and it won't start. All I get is a click and that's all. Seems to be if I let it idle back to normal before switching off the engine it works okay or if I just switch off engine then don't come back for a while it works. But for example, tonight I went to get petrol then when I filled up and got back into the car it wouldn't start for about 10-15 mins of trying, then tried once more and it started up.

So I either wait for 5-10 mins before switching engine off

or

Switch it off right away and then don't come back for an hour or something.

Any one know what this is, seems stupid that I can't do something simple like get petrol or call into the shop.