Should I polish the car myself?

If is is dull and you want it to shine polish it. Most cars have a clear coat with UV blocker , or the UV blocker is in the paint itself. My 2011 shines just fine if someone washes the dirt off of it ; it is garage kept . But my previous truck was parked outside and ,when clean, it also had an excellent shine ( 2004 year model). Most car finishes are now organic pigment colors rather than mineral pigments and deteriorate if not protected from UV . If your car did not originally have UV blocker , the appearance could be improved with some polish product , but it has had some damage already. This same UV deterioration can be easily seen in acrylic headlights ( auto finishes are mostly acrylic resins ) ; my 2011 lenses are "clear as glass" , but I see newer cars with yellowish cloudy lenses - poor UV blocker. Both the acrylic resin and organic pigments in the paint are deteriorated by UV.