Noise while rolling out

Hello, I am here for the first time and hope for help. Drive a Smat fortwo and for some time now a noise appears, not always, but only when rolling out the vehicle when it shuts down itself. At about 30km/h in the 3 gears the noise starts and stops in the 2 gears again. If you leave the foot slightly on the brake pedal the noise is transmitted. Was already three times in the workshop. Demonstration effect stayed out, then a luck, you could hear it, tip unbalanced the brake discs. Could still drive with it. Second attempt. When changing the bike from winter to summer, the brake disc showed glowing. Topic noise addressed, brake discs and laid down were changed. Full hope go, noise still there. Test drive, demonstration effect noise remained out. Quarter-hour before it was still there. Tip from the factory master gear. What now do ???? For a tip I would be grateful. 59hollywood