Standard reference works list 'spring' as a common noun, which does not, therefore, take a capital letter, so "I love the Spring" is wrong, but "I love the spring" is correct.
I prefer George Orwell's admonition to disregard any of the above rules if they result in poor English (not about Spring, but you get my drift).
If I write "I prefer the spring", it's not inconceivable that I like a coil of metal wire that goes boing when you push it. But if I write "I prefer the Spring", there is less ambiguity.