The date of that symphony, 1788, certainly accords with the literary discussions of romanticism. Rousseau's Confessions date from 1782 and Baumgarten's book from 1750. Hoffman was writing in 1813, speaking of Mozart in retrospect. Mozart's operas are even more romantic in their effect, especially The Magic Flute which seems to fit Gustav Schilling's definition of romanticism rather well: "[an] attempt to transcend the sphere of cognition, to experience higher, more spiritual things, and to sense the presence of the ineffable."
I think we can hear in this music, from The Magic Flute, if not romanticism as we usually understand it, then certainly some elements, some germs, that composers like Carl Maria von Weber would build on in composing what is usually regarded as the origin of German romantic opera: Der Freischütz.
What they have in common is the sensation of a glimpse into another world, a sense of the eerie or chilling. In my next post I will look into those elements in Beethoven that also had a big influence on the early romantic composers of the 19th century.