The first approach to the problem
The body is made up of modules which allow the overall motion of body, while (possibily) preserving their self-sufficiency and separation in the structure.
The bottom and top modules are identical and, together, allow a -30 +60 degrees inclination of the body.
The middle module is not self sufficient or separated from the top and bottom modules, but relies on their structure to anchor its driver element.
The second approach
The three main configurations of E-2?'s Body, from a side view.
This time the approach should be final, since the mechanisms involved in bending the neck are both defined and comprised of components we are already familiar with.
Perspective of E-2?'s Body, bending forward
Perspective of E-2?'s Body, bending back
The back-and-forward bending module and (over) the lateral bending module
Another perspective of the two modules