Single motor + Timer. Lift and reverse hand. Single joint robot arm
What are you asking? Are you trying to figure out the size of motor you would need? What components?

There are multiple solutions. Simply, you could attach a motor, probably a small gear-head motor so you could get enough torque, a limit switch or two, and maybe a timer relay to get the pause you are looking for. Simple, cheap and uses off-shelf components. 

Do you need the motor to reverse or can the arm just fall down? 

You could also build an elegant mechanism like this and have a motor just run continuously. from an electrical perspective, it would be simple:
Rocker Mechanism