People have rights, but not the right to infringe unnecessarily on the rights of others, in this case to also peaceably travel from place to place without undue fear of getting injured or causing injury.
The argument for seat belt rules touches the rights of others three ways. First, a person driving without a seat belt can more easily lose control of the car if they maneuver violently, putting others in danger. Second, in an accident people without seat belts get injured more easily, get thrown from the car into the path of other cars, and therefore can cause harm to another person either by their personal feeling about causing injury to the unbelted passenger, or running over or injuring a passenger thrown from the car.
Third and least persuasive is that either through taxes for people without insurance, or through higher insurance premiums in no-fault states, the increased injuries and costs to people driving without seat belts are passed on to others.
Now, you can disagree with all these, and based on that disagreement argue that the legislature has implemented a bad law. But the arguments are at least reasonable enough to merit discussion and to pass basic constitutional muster.
You do not have an unrestricted right to travel from place to place using the federal highway system built by tax dollars.
Yes, you do. As long as it is done peaceably.
Has nothing to do with seatbelts, booze, firearms, radios, chewing gum or anything else somebody gets all tumescent about banning or requiring.