Müller stepped up from karting in 1995, and finished third in BMW Formula Junior driving for Abt Sportsline. In 1996 he won Formula Renault Germany. Müller stepped up to Formula Three for 1997, finishing third in the German Formula Three Championship.

Müller stepped up to International Formula 3000 for 1998 driving as a BMW Junior for the Oreca team, but only finished in 20th position. He opted to race in the French Formula Three Championship in 1999, and finished seventh. He then returned to the German championship in 2000, and finished as runner-up to Giorgio Pantano, driving for Team Ghinzani. In 2001, he raced for the team in Euro 3000, and finished third in the standings behind Felipe Massa and Thomas Biagi. Müller returned to International F3000 in 2002, driving the first five rounds for Durango before moving to European Minardi for the next four rounds, but he failed to score any points during his nine races and separated from the team with three rounds remaining.

Müller tested with IndyCar Series team PDM Racing at the beginning of 2003. He competed at two NASCAR Craftsman Truck Series (now Camping World Truck Series) short tracks before the end of the season. He finished 26th in the #23 Team Racing at Indianapolis Raceway Park and finished 25th in the #07 Green Light Racing at Martinsville Speedway.

...
Wikipedia