I have spina bifida & I sit in a wheelchair & over the past few days the nerves in one of my legs has been making my leg slightly jiggle. Normal?

Spasms. Muscle spasms, or spasticity is common in spina bifida. It can become temporarily worse if you have a bladder infection, constipation, or a skin sore. See a neurologist or physiatrist to have it checked out. Antispasmodic medications (not just a 'muscle relaxant') can help. You may also need to treat an infection, constipation, or skin sore, if present.
Sacral lipoma? Many patients with spina bifida have or have had sacral lipomas. These can grow and irritate the nerves within the sacral sac that can produce strange feelings and movements in your legs. A MRI of your lumbo-sacral spine may be appropriate to compare with prior studies. Just irritation of the sciatic nerve through your buttocks can produce similar problems. You may need better wheelchair seat.