The Supreme Court agreed to decide whether cars must be equipped with air bags or automatic seat belts - perhaps as soon as next year - or whether the Reagan administration can kill the new equipment rule.
The justices will hear an appeal by the administration and auto manufacturers of a ruling ordering all cars made after next Sept. 1 to be equipped with ''passive restraints.''
In another case, the justices without comment refused to step into a dispute over how to handle the huge number of death and injury lawsuits filed after two skywalks in a luxury Kansas City, Mo., hotel collapsed and killed 114 people.
In other action today, the high court:
* Promised to decide whether a South Dakota man should serve the rest of his life in prison for writing a bad check for $100 and other nonviolent crimes.
* Agreed to hear a case touching police stations across the country - whether police can look inside a purse when booking someone into jail.
* Accepted for argument the Florida death sentence of Elwood Barclay, who joined in what one judge described as the ''random racial hate murder'' of Stephen Orlando, a white teen-age hitchhiker, in Jacksonville Beach, Fla., in 1974.
* On a 6-to-3 vote in an obscenity case, left intact a court order declaring a Tallmadge, Ohio, adult bookstore a moral nuisance and barring it from selling any more erotic materials.