Bartels started karting in 1982 and in 1985 he won the German karting championship. Moving to single seaters in 1986 he promptly won the German Formula Ford 1600 title.
For 1987 he switched to FF2000 finishing third before another move up the following year into Formual 3.
Two seasons of F3 saw him finish 5th and 4th in the points before another upward move into F3000 in 1990. That year he also participated in the World Sportscar Championship with Porsche.
Starting 1991 in F3000, mid season he joined the Lotus F1 team as a paying driver in the second car. Unfortunately he failed to qualify for all four Grand Prix he entered. He then continued in F3000, finishing 4th in 1992, before switching to the DTM, where he was the top privateer in 1994 with Alfa Romeo and also raced the series in 1995 and 1996.
In 1997 he raced in the ADAC STW Cup with Opel and in 1998 with Peugeot. In 1998 he also drove a Porsche 911 GT1 in the FIA GT Championship with Zakspeed.
Driving for Audi in the STW Cup in 1999, he finished 7th overall in the series and won the Macau Touring Car Grand Prix.
Returning to the DTM in 2000 with Opel Team Phoenix, he finished on the podium twice to end the year in 7th place overall and 2nd in the Teams Championship with Manuel Reuter. He also won the ADAC 24 hours at the Nürburgring.
Two more seasons in DTM with Opel and another win in the 2001 ADAC 24 hours at the Nürburgring then saw Bartels switch to V8STAR Series with Team MB Racing Performance Vitaphone driving a Silhouette Opel Omega in 2003.
In 2004 he joined Uwe Alzen in the Vitaphone Racing Team Saleen S7-R.
He currently races for Vitaphone Racing driving a Maserati MC12 in the FIA GT Championship, with great success alongside Timo Scheider in 2005 and Andrea Bertolini in 2006. He dated Steffi Graf for seven years.