All Behance profiles are visible to the public, so unfortunately this is not an option. You can restrict the ability to view projects by changing the privacy options in the project itself, but your profile still will be searchable in google, etc.
On Behance, you can restrict access to any project by making it private. You can do this by going to Edit Project --> Settings --> Click Edit next to Projects visible to-->turn all OFF. You can give certain Behance members of your choice access to restricted projects in Limit Visibility, but there is not "password protect" option for the general public.
On Adobe Portfolio, you can password protect any project or page of your choice by going to Settings --> Site Password. This will allow you to share your private projects or site with clients, or anyone else you give the site password to.