The electronic throttle is the place to start. If cars arent used fairly intensively you get problems with the throttle position sensor.
Might sound daft but I'd be inclined to sit in the car in the garage engine off, and depress and release the throttle a hundred times just to make sure it was working as well as it can. On the Lotus there was a procedure for re-calibrating it which I think was no more than ignition on but engine not started and pressing the throttle fully open and fully realeased a couple of times. Ignition off then start the engine.
If the problem persists then garage and diagnosticks.
