How to use Rules send an email with a list of nodes that fill certain conditions?
When you want to run a rule periodically, use the event Cron maintenance tasks are performed.

This will trigger your rule whenever cron runs.

See the cron documentation on drupal.org for more information on cron and its configuration.

Because this action doesn't specifically involve nodes, the next problem is loading the nodes you want to act on.

How you do that depends on which nodes you want to load the nodes. Examples are (there are likely also other ways):


The Load a list of entity objects from a VBO View action that is provided by the Views Bulk Operations module. This was you can set up a view that lists the nodes you want to target and load the nodes from that list.
The Fetch entity by property action. This could be used to fetch all content of a given content type.


When you have a list of entities you can loop add a loop to your actions to loop through the list and perform actions on each entity.

If you need to check perform conditions as you are looping through (like checking the value of a field on the entities) you can use the Conditional Rules module to add if blocks.