Several bad ideas there:
Please: Never allow a snake loose in your car while driving- they don't usually stay on your shoulders for long- & they HAVE actually caused terrible vehicle accidents when they grabbed onto the steering wheel or proved distracting in other ways, like choking the driver. Please don't make it into the news that way- it reflects poorly on the whole snake-keeping community, & if we don't keep ourselves "in line", others happily will. Know what I mean? Distracted driving isn't just about cell phones- you can get a ticket for that.
Taking your pet snake into the reptile store is not the best idea either- the danger is that your snake will pick up snake mites, & they're a big hassle to treat, also a health & longevity issue for your snake (mites may be vectors for diseases, or the side effects of aggressive treatment to get rid of mites has been known to injure or even kill snakes).