Q. I have a 14 year German shepard she hasn't been able to get up without assistance what could that be?
A. When pets get older, their bodies can become stiff and painful, much like ourselves. It is pretty common, and some days are worse than others. Weather and temperature can effect this as well. 14 for a shepherd is getting pretty old, a breed with tendencies for many common bone/joint problems. I would suspect this is the problem.
There are things you can do to help (to a point) like adding a ramp or pet stairs to make going up and down easier, a good memory foam bed to soothe achy bones, glucosamine will help lubricate her joints so she moves a little easier, your vet may be able to offer some pain meds for the bad days but these are all temporary solutions