After restarting the odoo service, a database wil only be loaded after accessing with http or the scheduler wil not be activated.
How can all the databases be loaded automatically (without accessing the database through http requests first) after restarting the odoo server?
Databases don't need to be loaded. What is it that isn't working. Once you restart the server you have the same state as you had when the server was running.
For example, scheduled fetchmail tasks are nog executed right after restarting odoo. You must first access odoo web.
I would upgrade base to make sure the database version matches the repository version. I don't know of any reason why you would need to access Odoo via the web client after a service restart. We have several clients who restart their services periodically as part of refreshing idle PostgreSQL connections and who don't report any issues with fetchmail.