2007 Jaguar X-Type Problems

hi all When i try to increase the speed during driving , the throttle does not respond and the car start jerking for awhile. I sent the car to workshop for check up they change the fuel pump but still the same problem. I'm seeking your he...

when cold the car starts first go and runs perfectly when the engine gets up to temp and I stop for a few mins when I come to restart it takes a few go's before it will start ,its quite lumpy for a few seconds before it settles down at abou...