No, readers on auto-renewal will not receive an email before the renewal. They will only receive an email after the payment is made. Only readers on trials will receive an email before the subscription renewal (a week before the trial ends).
The trial email will have the subject line of "Your Subscription starts soon" and a body like the following
Your trial is almost over. Your subscription to EXAMPLE PUBLICATION will automatically start on September 25 for $3 per month.
If you wish to cancel, you can review your subscription details by clicking here or by visiting EXAMPLE PUBLICATION DOMAIN and clicking
on our logo in the bottom-right corner of the window.