Does creating a folder start a workflow?

Does creating a folder cause a workflow to run?

Yes, when you create a folder, SharePoint treats it like you are uploading a new document.

If you only want to run a workflow on documents that are created or changed, you will need to add a step to your workflow.

The workflow condition would be:

If Current Item: Content Type equals Folder

Stop workflow

Doing this will stop the workflow each time a folder is added or changed.