The German, who has seven championship titles to his name, has said that he "didn't really feel like" continuing to race after his Mercedes contract expires at the end of the current year, with his place in the team taken by Lewis Hamilton.
"If I wanted to stay I had options to stay, but I didn't really feel like it, quite honestly," Autosport quotes Schumacher as saying.
"It is very clear what comes next. Six races to go. That is what comes next.
"Whatever comes after, we will see. There is no point or any need to find any decisions right now, and I will do it exactly as I did it the first time."
As well as seven championships, Schumacher has 91 Grand Prix wins during his career.