Pinched lumbar nerves. Any negative side effects to long term mechanized traction to relieve pinch nerve?

No, not Realy. As long as mechanical stretch gives you productive hours in your day, it is a good technique. If you forgo stretch of your legs, conditioning and strengthening exercise you will not achieve full recovery. When you know you have bad discs, avoid prolonged sitting, driving, and jarring sports which lead to chronic facet problems (arthritis) in the back. Inversion techniques / yoga mimic traction.
No. No long term side effects. Try inversion table at home. Just realize that this is a treatment option and not a method to cure the compressive pathology.
No. But a few thousand dollars later the overall result will likely be the same as with conservative therapy. Find a board certified pain physician and insist on comprehensive treatment which includes physical therapy.