About a month ago Google announced that they were
Adding an autosave alternative to Google Forms. The option to save work in progress in Google Forms is rolling out to all users over the next couple of weeks.
my short video to see how it works..

More Google Forms Tutorials.

Applications for Education.

Saving Google Forms responses in progress has been a function that teachers have requested for as long as I can remember (and Ive been teaching with Google Forms longer than the majority of intermediate school trainees have lived). Trainees will no longer need to begin over if they get disconnected from the Internet or the bell rings to end class before theyve finished answering all of the questions on a Google Form.
There are some circumstances in which you may not desire trainees to be able to come back to a Google Form to finish it after theyve started. For instance, a student purposefully taking a long time to answer test questions so that he/she can go back to it later after searching for answers. Because case you can disable the autosave choice on that particular kind.