This movie features a character named Vincent, played by Vincent Price, who is the sole survivor of a plague that has wiped out most of humanity. While he doesn't travel back to slavery days, he does have flashbacks and hallucinations that transport him to different historical periods, including a scene where he finds himself in a slave auction.
It's important to note that the movie doesn't explicitly focus on slavery, and the scene involving the slave auction is brief and serves more as a visual metaphor for Vincent's isolation and the horrors of the past.
If you have more details about the movie you're thinking of, like the main character's name, specific plot points, or the time period it was released, I might be able to provide a more accurate answer.