Hi Pete49
I think Joules has hit the nail on the head. Set the current for the motor with the pot on the stepper driver. You can usually do this with a meter, by adjusting the tiny potentiometer. Value should be set approx 15% below rated motor current. Only other thing to check is the jerk value in Marlin. It defaults to 20mm/sec but it may have been altered. You can find it in configuration.h after the acceleration and speed settings.
Hope this helps
Best Regards
picclock