I would take some tape and outline the area to protect the surrounding paint.
Then take a heat gun (low heat) or blow dryer (medium heat) and wave it over the sticker for about 15 seconds (keep them both moving).
Then take a pencil eraser and rub off the sticker. That's why the tape is there, to protect the surrounding paint from the abrasive eraser. Rub for 15 seconds, then more heat, then rub again.
If this doesn't do much good, then goo-gone would be the next step.
If the goo gone take off most of it, but not all of it, go back to the eraser.
Don't be tempted by using a razor blade, although for uncoated glass that would be useful.