It really depends on what they actually are. That sounds like a job for a heat gun on low and a plastic scraper. Butter wet wax can take care of some adhesive residues and maybe might help. Then there’s always a nice acetone soak. Be very careful (I mean just don’t) with heat and any solvent because you’ll light a nice big fire and burn your house down.

If you’ve got decals on paint there’s always a risk you’ll strip both off at the same time.

A 3M stripe off wheel might also help, but do your research on any of these.