Automatic chage password of pages after some time

Welcome to WPSE. Plugin recommendations are considered off-topic here, so here’s an action approach to the problem.

You could use WP Cron to schedule a daily event for resetting page password. You can use wp_schedule_event() to schedule your custom event.

In your event callback, use first WP_Query with password parameter to get all protected pages. Then loop through found pages and update their passwords with wp_update_post as password is saved in the post_password post property / posts table column.

If you want the new password to be something random, you can for example use wp_generate_password() to generate it.