By default it depends how you call your Seikret, if you press Up it uses auto-pilot if you press Down it's manual, and you can of course switch between the two while mounted
It was one of my favorites. Not only can you go manual like others said, but you can do other chores while it drives for you. And I really hated getting lost in the ancient forest, so anything that prevents that again is a plus for me. Especially if the beta frequency of monsters running wasn't overtuned like the weather changing.