Create a pager between fields
If you can use Views, it'll be simple.

Views can provide each field's value as a row. Set it up to display fields, add your multivalue body field, filter by node id, and you can set up views pager to show one row per page.

Then, use Pathauto to create nice addresses for nodes of that type, like /multibody/[nid]. In views, use the same address and voila - node pages got overriden with your view. Use Global Redirect to redirect from /node/[nid] to /multibody/[nid] to make sure users will not end up reading whole node at once.