We don't support adding a table of contents with links, but you can add plain text to the form page if you'd like to start with a basic summary. You could also edit the pagination buttons to show a progress bar or page numbers, if the form has multiple pages to show how far along the submitter has to go.

Our Form Editor does display a table of contents on the Question panel for ease of editing. This is not visible in the live form.

Table of Contents in Question Panel