Problems with Stepper motors

Hi all,

this is my first post. I just completed the build of my Prusa I2 with Ramps 1.4 and Marlin firmware, on the PC I use Pronterface.
Now I a have a strange behaviour which looks like the following.

After I enabling and conntecting my Prusa I2 to the PC I can move all three axis, so far so good.
When I then press homing all axis only the x-axis moves to home position. I already checked the other two endstops with M119 and saw that the others are correct, which means not triggered.
The new funny thing is when I move one of the axis for a mm ( doesn matter which) all three moves at the same time.
When they stopped after 1 or 2 sec, they will not move again untill reset.

Any ideas ?

Thanks

If you press the endstop (assuming mechanical..) and try to home, does it move? could be you need to reverse the mode your end-stops are operating in.

Yes they are mechanical endstops. When I press a endstop and try home it doesnt move.

Care to attach your configuration.h file?

Weird motor motions often turn out to be a short in wiring - motors and/or endstops. Repeatedly check the endstops - M119 by repeat triggering the stops with your finger. Check through your motor connections and splices. Be sure your stepper drivers are adjusted with enough power for the motors to move.