motor starts when plugged in

Hi.
I plugged in the power supply cable of the motor and it unexpectedly started rotating at very high speed and without any command from the software (even not connected with the computer). I guess it is executing a previously loaded program (if it has some internal memory or s.th.). I remember that when I installed it the first time, I run it in velocity mode.
How can I make it disregard possibly stored commands before to switch it on?
Thank you