1991 Volkswagen Polo car judders/almost cuts out when starting/initially driving

I'm finding that a lot of the time my car is shaky to start and almost cuts out when it does. I have to really rev it to keep it going. I'm also finding that when it does start it will almost lose power within the first five or so minutes of driving and start juddering along for a few seconds. I find that it doesn't cut out completely and I don't have to start it again but it doesn't respond to accelerating for a couple of seconds. I find that the only way to get it going/ keep it from stalling is to keep my foot down on the accelerator until it passes. It always seems to run fine after I've been driving for 5 minutes or so. Does anyone have a clue what it could be?