Renault Clio 1.2

Hi, Renault Clio 1.2 16v, 2003, 42000 miles. If I start car from cold it runs like a dream. BUT, if I make a journey, switch engine off, then back on again within a few minutes the engine starts up idling at about 2000rpm and the accelorator doesn't respond. I have to wait half hour then try again and then it works fine! Got two yellow warning lights that randomly come on / go off. One is the diesel temperature light (but the car isn't a diesel!!) and the other is the poisonous toxic fume warning light but I don't think that my model has got this facility!
Help please:)