We would like to drop off a rental car in Orvieto one morning in June and travel by train to Sorrento to stay that night stopping in Naples to see the archaeological museum along the way. Is this feasible? Where would we store our bags while touring the Naples museum?
Drop your car as planned, catch the 08:05 train to Termini, then change to the high-speed Frecciarosso, departing Termini at 09:45. You will be in Naples by 10:55. Store your luggage in the Naples station and head to the museum, a short metro ride away. Spend a few hours in Naples (See Rick Steves' Naples self-guided day in his Itlay guidebook), and when you are tired of Naples, take the Circumvesuviana to Sorrento. It takes about 75 minutes to get to Sorrento.