Research scholarships are recommended for smaller research projects, for the years just after finishing the PhD or for transition periods. The response period for a scholarship application is often shorter than for project funding applications, and there are some special scholarships for working at special libraries or on selected topics. Another good reason for a scholarship is a research stay abroad.
Scholarships are typically tax-free, but also do not include any sort of social insurance – you must arrange health and pension insurance yourself and do not earn the right to receive unemployment benefit (Arbeitslosengeld I). For these reasons, a scholarship cannot be the regular type of funding for the postdoc phase.
You can search for scholarship announcements in the databases.