After a full work day, I swear I feel numbness in my arm and shoulder.

I used to get pain in my wrists and the numbness from reduced circulation from sitting in one place all day.

get some exercise after work, you don't have to kill yourself but you should try and walk 5 miles a day overall or run 3 to stay in decent health.

extra necessary when the work is sedentary.

Take short breaks throughout the day. Stand up and do light exercise for example with a stretch stick.