Twenty-second Amendment to the United States Constitution
The amendment prohibits any individual who has been elected president twice from being elected again. Under the amendment, an individual who fills an unexpired presidential term lasting greater than two years is also prohibited from winning election as president more than once. Scholars debate whether the amendment prohibits affected individuals from succeeding to the presidency under any circumstances or whether it only applies to presidential elections.
2017 German presidential election
Every member of the Federal Convention (members of the Bundestag and state electors, once they are elected by their respective state parliament) can propose candidates for the presidency. It is required that the President is a German citizen and at least 40 years old. Every candidate has to declare their consent to running. Candidates can be proposed before the Federal Convention and (theoretically) during the Convention before every ballot. If the President-elect is a member of a legislature or a government on federal or state level, he has to resign from that office before the start of their term. A sitting President is not allowed to run for a third "consecutive" term.