Engine Dies

Car is a Primera 2.0 GT - 1997.
Running at speed the car runs fine, but having stopped and trying to pull away problems occur. Hit the throttle quickly and the revs will die until usually the car will stall. Very very gently on throttle and you can just about pull away without stalling. Makes driving very stressful as you always need big gaps in traffic.

I've change the plugs and HT leads and looking to do the distributor cap this week; as I read elsewhere this may help. Will this fix it or am I on the wrong road !!
Any advice appreciated.

Also notice a symptom whereby you turn off the lights and the revs dip to about 200 and then recover - huh ??? :eek:

Could even be belts slipping or loose, maybe? I'd have checked the alternator first in that sitch though..

Doofs