A center drill is the thing to use to start a hole, without a jig.
Now if you have a cube of metal, a drill press and a vise it’s really easy. You set the vise so the part is roughly in the center and drill either the diameter for the pin or the shaft diameter. Then flip the cube 90 degrees and drill the other. Now you stick the motor shaft in the hole it fits in and run the pin drill through the other hole and it will be right in the center.