Motors jerk and move when 3d printer powers up.

[mendel...@gmail.com]

I have converted my 3d printer’s X and Y axis to run on mechaduinos.    

I have  observed instances when the motor jerks a small distance when the printer is powered up.  

I also noticed that sometimes it moves also quite a distance.

Why is this happening and is there a way to eliminate this?

Thanks for any input