Getting up gingerly and for short periods sounds like pain and could be spinal pain (disk disease). Assuming she is not currently on any meds (if she is what?), you could try giving her a single adult strength (325mg) aspirin. If it helps, pain is likely the problem. If not, it could still be pain, but could be something else.
Electric shock is another thing that will make dogs scared to move. Stray electricity is once source. Are there any bare wires or does she tend to mouth cords?
Is she eating and drinking normally if you take the food to her?
Has she urinated and/or defecated?
When she gets up, how does she hold her head and tail?
Let me know the answers to the questions and any follow up questions you have at this point.
Pain would be high up on my list of possible causes from what you say. The head down, don't want to move is common with neck pain. Just scared of something is possible, but not likely in an adult lab.
Can you encourage her to get up and go out to the bathroom? If you live in an apartment and this involves stairs, I would probably try putting newspaper down instead and hope she was once paper trained.
Aspirin today and the vet tomorrow would be a reasonable way to go. If she becomes unable to use her legs, an emergency vet would be indicated.