Ok, so you've triggered my personal bugbear with Yoda. Time for a rant. Let me explain:

Yoda was pitched to Luke on Hoth as the Jedi master who trained Obi Wan. Luke (and us as the audience in 1980) had this expectation of a wise old man if he trained Obi Wan. When Yoda pulls Luke's Xwing into the swamp and meets with him, he puts on a "Little Creature" persona to test Luke's patience. Anakin was famously impatient. Yoda hammed up his speech mannerisms to 11:
"Away put your weapon, I mean you no harm"
"Help you, I can! Yes! Yes!"

Once Luke fails this test, and we get to Obi Wan, Yoda drops that whole act.
"I cannot train him. The boy has no patience."
"Too old! Yes! Too old to complete the training."
"A Jedi must have the deepest commitment, the most serious mind. This one, a long time have I watched. All his life has he looked away! to the future, to the horizon. Never his mind on where he was! What he was doing!"

Then once we get into training, we get the bombs of wisdom:
"For my ally is the Force, and a powerful ally it is. Life creates it, makes it grow. Its energy surrounds us, binds us. Luminous beings are we, not this crude matter. You must feel the Force flow around you. Here, between you, me, the tree, the rock, yes, even between the land and the ship."

You see? Yoda retained a little of that vocal mannerism - easily explained as someone speaking a different language to his native one. For the most part though, his dialogue was pretty natural.

But then people spent the next 20 years doing Yoda impressions of his little crteature act. So by the time of the prequels, it was expected that Yoda would talk all backwards. So the prequels had him doing that backwards-talk throughout. I hated it then, and I hate it now.

It's a crying shame that people coming to Star Wars never get their expectations of Yoda subverted today as we did. Yoda is just too pervasive in our culture. Even my own kids who I tried to shield from all that instantly recognised Yoda when he came on screen.