Reduce heat dissipation in Stepper motor
60C is not an unusually high temperature for a stepper motor, though it is hot enough to surprise somebody who doesn't expect it.

If you want the motor to run cooler, then you have two options, and you can use both.

1) Improve the removal of heat from the motor. Mount it on a heatsink, or blow a fan at it.

2) Program the stepper motor driver to deliver less current to it in the hold, this will however reduce the hold torque. If that's not sufficient, program it to deliver less current when stepping, this will however reduce the driving torque.

Option 3) Stepper motors are very inefficient, and get hot. Replace it with a conventional motor, either brushed or BLDC, servo-controlled if you need accurate position.