When I sit I get pain in my lower neck and pain shoots down my arms?

Impingement Issue . This is most likely an impingement issue where something is putting pressure on the nerves at their exit point from your neck. Could be due to arthritis in your neck bones, cervical disc issues, some bony growth that pushes on the nerves, or tumor. Sometimes, irritation of the muscles and spasms of the neck can cause issues. A thorough exam and testing of sensation and strength is suggested.
Get checked for. Arthritis in your neck spine and pinched nerve. (this is a common condition in the golden years. Enjoy it & make the most of your twilight years !).