I used to work with the Como 3.0 for many years and this was a common problem. The bike moves on its own at 3.3 mph because there is a walk mode that Specialized does not advertise built into their bikes. It is activated by pressing and holding the plus button and should deactivate once you release that button. However, it is common for these buttons to get stuck and can even create a drag resistance while riding as you were fighting the motor. The only permanent solution I have found for this is to replace the headset which is about a $100 fix, but the quick fix is to press the plus button a few times followed by the minus button. If the power level changes, the the plus button is no longer stuck and walk mode is disengaged.
I hope this helps!