There's a very similar thread a little way down the page started by Hobojangles with what appears to be essentially the same problem with an MZ-M. J. Scott had this answer:
Originally posted by J.Scott The manual says that the film auto-rewinds at the end of the roll.
Just a couple things to ponder:
-perhaps the 'mid-roll rewind' button is stuck in the 'on' position.
-have you tried different rolls of film? For some reason that roll may be wound too tightly and the camera is sensing this and rewinding.
I'm wondering if there's an issue with the mid-roll re-wind button; maybe it's on (and it shouldn't be) or it's malfunctioning in some way.
Best,
Kevin