You will have to give a bit more info, also I am presuming you are meaning the spindle starts on its own, or do you mean the axis start moving?
If its the sindle then info on how it is normally ativated would help, ie is it a relay that switches it on, do you have a custom macro or use a brain for this? any other info you think might be usefull as well.
Might also be an idea to attach your xml file and any brains or macros that you use for the spindle.
Hood