Electronic transmission control module".

I have a 2000 Z3 .......40000.miles........The Electronic transmission control module". indicator comes on occasionally saying there is something wrong with the auto tranny ,once I reset by the book .......this involves , placing in Park setting the hand brake for 20 seconds ,and then restarting.... ....this clears the light on dash for maybe 2 to 10 starts ,then the light will come on again. this does this only on the start ,never when driving ,and after it comes on everything works as normal. If you can help me out ,please e mail me your phone and I will call you Thanks in advance Dave Please reply to drice003 AT woh.rr dot com