How I can fix my Vauxhall Corsa 1.4i M Reg?

My Vauxhall Corsa has been driving me up the wall for about 3 months. When I get stuck in traffic it gets warm quite quick and then the Engine Management light comes on. It loses power and grinds to a halt. It will not start straight away, I leave it for approximately 60 seconds then it fires up straight away. It had a new head gasket last summer, cambelt. timing belt and a full service recently as well. I have taken it to my local garage and when they have it it seems ok. Any feedback is greatly appreciated