In his letters to the Corinthians, Paul makes it clear that he expects to be rewarded for his work. And not just by God after he dies. He thinks his followers owe him a material reward for his spiritual work, just like any other worker would get. And he says that isn’t just his opinion. God’s law (at least the way Paul interprets it) commands that people pay others for their work, including preachers.
But then he claims that he’s not preaching for profit, that there’s nothing wrong with not paying a preacher, and that he’s not trying to convince anyone to give him anything. So why was he just telling people they owed him, then? Even though he thinks he has a right to be supported by his followers, he now says he would rather die than use that right, because he’s proud not to be a burden to the people he’s preaching to.1
Then he says he doesn’t even deserve a reward, because he can’t help preaching. So why was he just saying he did deserve it? For Paul, preaching the gospel for free is its own reward, and other than that, he doesn’t want any reward.
Paul saying he would rather die than get the payment he deserves makes a little more sense when you remember that he doesn’t really care if he dies or not. But that’s not enough to fully resolve the contradiction.
A better explanation is that Paul must just not care what God thinks. That’s the only way he could be so against being paid for preaching, when he thinks God has commanded that people have to be paid for preaching.