I want to start learning the cello and I need some advice...?

I'm 17 years old and I really want to learn to play the cello. I'm
thinking that I just want to teach myself, but I don't know if that's
a good idea. I play the piano, so I already know the treble and bass
clefts. And I took a year of violin when I was 11, so I know how to
hold the bow. So, knowing all that, is it a good idea to just teach
myself to save money? Or should I try to find an instructor?