My wife has pain, weakness and some paralysis in her legs especially after working. She has had neurological tests done that turn out OK (nothing wrong). Most of the pain is at night. What might be the problem?

Working at what? Moving around, or standing in one spot? How old is she? Is she overweight? How's her BP?
I would have checked her vascular system, specifically the inability of her legs to send blood back up to the heart from all sorts of conditions falling under PAD, peripheral artery disease. Do you really mean paralysis? Or cramps, or numbness ('falling asleep')? In both legs equally?

I saw your message to me and would appreciate it if you will copy it here for all to see and answer. Thanks.

She moves around, working in a grocery store, early 40s, not overweight, good BP, and see has been checked for circulation in her legs and was told it was good. She has trouble getting them to start moving and complains of a heaviness felling in both legs equally.

I can't move very well when I get up in the morning, but I'm 66 and overweight. It's very common after a night of lying down; circulation has to get going, and as you age it gets slower and slower. The valves in blood vessels farthest from the heart have the most work to do, and they often weaken as we age.

Grocery jobs, even moving around, mean a lot of bending forward just enough to put a strain on the knees and ankles and feet, with the knees locked and the ankles bent. She might have muscle strain from all that, with the muscles tightening while sleeping.

I have had 'heavy' feelings in my legs most of my adult life, and often wondered if it was related to estrogen levels. I've read various accounts of connections to things like spider veins. I think the science is inconclusive.

Suggest that she soak in the tub before going to sleep.
Is your mattress too hard or too soft, I wonder?
Can't think of what else. Join a gym or yoga class.
I think the medical tests have covered everything in the usual realm.