Shifter is sometimes difficult to move to reverse (very cold here now) and vehicle does not move when in reverse???

This maybe a case of a shifter mechanical issue that just requires lubrication, or it may be a shifter cable which is most common. We would need to remove the cable and see how the shifter operates without the cable attached to make this decision. Please contact us and we will set up the diagnostic procedure for you. Sterling Car Care 586-939-0230