Hi i have almost the same problem with my partners 1994 micra, will drive beautifully for up to half an hour then will start juddering, engine will cut out etc. is worse when starting off ie pressing harder on the gas. had the same problem 18 months ago, AA came out, couldn't find a problem, then it just self resolved. is a real probelm at the moment. the two things i think it could be is
1. the fuel pump ? a bit of dirt in there
2. Air mass meter
I don't know but these are the possibilities looking on the internet. problem is we can spend £100's in paying a garage to diagnose a problem. my email is mjalbert1@gmail.com, if you find an answer do let me know, and if i get and answer I'll let you know.
Mike
Mike Albert, July 2007