"Germany always has coalition governments and it was always stable," he said in English on Monday, standing beside a statue of Willy Brandt, a Cold War-era SPD chancellor awarded the Nobel Peace Prize for fostering dialogue between East and West.
The SPD, Germany's oldest party, won 25.7 per cent of the vote, up five percentage points from the 2017 federal election, ahead of Merkel's CDU/CSU conservative bloc on 24.1 per cent, provisional results showed.
The Greens came in with 14.8 per cent and the FDP won 11.5 per cent.
The SPD's recovery marks a tentative revival for centre-left parties in parts of Europe, following the election of Democrat Joe Biden as US president in 2020.
Norway's centre-left opposition party also won an election earlier this month.
Mr Scholz, who served as finance minister in Merkel's outgoing "grand coalition", said a government led by him would offer the United States continuity in transatlantic relations.
"The transatlantic partnership is of essence for us in Germany ... So you can rely on continuity in this question," he said, adding it was important for democracies to work together in a dangerous world even allowing for occasional "conflicts".
Mr Scholz said he hoped to agree a coalition before Christmas, "if possible".
However, his conservative rival Armin Laschet, 60, said he could still try to form a government despite leading his CDU-CSU bloc to their worst ever national election result.
The parties will start sounding each other out on Monday about possible alliances in informal discussions.
Ms Merkel, who did not seek a fifth term as chancellor, will stay on in a caretaker role during the coalition negotiations that will set the future course of Europe's largest economy.