Live TV images showed heavy smoke coming out of Rast’s car on the starting grid, putting a question mark over whether he would be able to take part in a race where both his main title rivals qualified further down the grid.
Team Rosberg mechanics discovered a fire in the engine bay upon opening the bonnet, but they were able to extinguish it with a piece of cloth and a bottle of water before the car sustained any serious damage.
Rast went on to claim victory after executing a brave double pass on the BMWs of Timo Glock and Sheldon van der Linde at the start, boosting his chances of lifting a third DTM title.
Asked how it felt to take the win after his starting grid scare, Rast said: “Yeah, it was a crazy story. As we parked on the grid with smoke coming up.
“We opened the bonnet, there was fire coming out. At that moment we thought the race was going to be over. But somehow my mechanics kept cool and got it under control.
“Then the start obviously from P3 to P1 for the first corner was the key for the success today. I got almost hit by Timo [Glock] who got spun around [after contact with Ferdinand Habsburg] and was very close behind, so I lucky on that side again.
"The end result was perfect. Now we are 10 points behind Nico [Muller], we reduced the gap by over 35 points [over both Zolder races]. Now we are back [in the title race].”
Rast believes parking an already overheated car on the grid may have caused the fire, although this is yet to be confirmed by Audi.
"On the way to the grid you try to warm up the tyres", Rast explained. "You do that by accelerating and driving very slowly. With cold tyres you can't drive so fast. This doesn't exactly cool the car down, but if you constantly step on the gas, the car gets pretty hot."
Rast was fortunate that he was able to complete his pitstop before the safety car was deployed after Robin Frijns' crash at the pit exit, allowing him to retain the net lead of the race.
The German driver says he didn’t pit in anticipation of the safety car as the plan had always been to stop a lap after the Abt driver.
“No, actually just lucky,” Rast said when asked if Frijns’ crash played any role in his pit strategy. “We didn’t really talk on the radio. I got the board that after basically Robin came in, so we tried to overcut him or not get undercut by him. Then he crashed at the exit of pitlane.
“I don’t know if there was a yellow flag or they were allowed to talk to me, but they didn’t. Just heard it when I entered the pitlane that there was a crash.”
Following his double Zolder win, Rast now sits second in the championship, only 10 points behind standings leader Muller, with Frijns slipping to third after his first DNF of the year.