Hey mine was doing exactly the same thing. The electrics are all on when it dies so obviously not electrical and it starts up again.
I let the bike warm up a few minutes before I ride and take it easy on the rev's while changing gear from first to second it doesn't happen! Go figure...
I'm new to riding bikes (although I've grown up as pillion with bike enthusiasts) so I'm sure there's a simple explanation from more experienced riders. Probably flooding the engine? I haven't a clue!
Sam :), January 2009