This is a helpful discussion among three noted traditional dispensationalists about the history of dispensationalism. While it is not about pretribulationism per se, at 9:45, one of the participants claimed that Paul believed in an any moment rapture (i.e. imminence) when he included himself (“we”) in the rapture in 1 Thess 4:15–17.
“For we tell you this by the word of the Lord, that we who are alive, who are left until the coming of the Lord, will surely not go ahead of those who have fallen asleep. For the Lord himself will come down from heaven with a shout of command, with the voice of the archangel, and with the trumpet of God, and the dead in Christ will rise first. Then we who are alive, who are left, will be suddenly caught up together with them in the clouds to meet the Lord in the air. And so we will always be with the Lord.” (1 Thess 4:15–17)
The fact Paul believed he could experience the rapture in his lifetime, does not logically follow that he believed it was “imminent.”
Pretribulationists are notorious for using this fallacious reasoning. Paul simply believes that in his lifetime the rapture may happen—not that it is “any moment.” And this is precisely what prewrath teaches: Jesus can return during any generation, including the first generation. The prophesied events that must happen before the second coming can all occur within a single generation.
There is nothing in 1 Thess 4:15–17 that indicates that the rapture is imminent. It is assumed by pretribulationists.
Ironically, in Paul’s second epistle to the Thessalonians, he explicitly states two events that must happen before Jesus’s return.