juddering

[Dman8a]

hi guys i have a 1.0i 12v corsa b 2000 on a W plate. every so often whilst slowing down the rev needle will drop below idle and the engine management light will come on and unless i manage to use the accelerator the car will stall and i have to put revs on to start the engine again and as i drive along the car will judder and not run smoothly. then when i come to start the car the next morning it will start but the engine will judder as if not using all cylinders, but other times the car will just run fine as if there has never been a problem i am wondering if it is a sensor that has gone which will only bring the problem on every so often.

Any help is much appreciated. thanks.