Hi have a little problem and was hoping you tallented folks could help me

the last week has seen my the car enging cut out now and then at traffic lights
its fine driving but as soon as you stop the revs now and then try to drop and the engine shudders and it quickly goes back to normal idle but every day maybe twice it will drop and just cut out it seemed like a isle valve problem but am sure this model dont have one

so is there a simple solution?

many many thanks