Transfer from Rome to Sorrento

Unless you have a reason that you don't want to train to Sorrento it is easy to do. The regular FS train is in the upper part of the station and the lower part has the small train to Sorrento. Once in Sorrento you can take a taxi to your accommodations if it is too far to walk. Care must be taken in the Naples stations due to excessive pickpockets and people dressed in blue pretending to be FS staff but it is not difficult to find your way. Head up walk with a purpose is usually all it takes. You can book your Rome to Naples FS trip early but I have never found it necessary to prebook in Italy.

There are several trains each day from Roma Termini to Napoli Centrale. Once you arrive at the train station in Naples, go downstairs and take the Circumvesuviana train to Sorrento. It's very easy to do, just beware of pickpockets in Naples and on the Circumvesuviana train. Trenitalia or Italo train tickets are usually cheaper when bought in advance. Circumvesuviana train tickets are cheap, if you don't mind riding on a dumpy train with coaches like old subway cars.

If the Circumvesuviana train worries you there is also the Campania Express “ tourist train”
Limited schedule so timing might not work

Or fast train to Napoli Centrale then driver to Sorrento for about 100 euros
We used this company
https://www.topexcursionsorrento.com/?portal_referer_id=46

Info here
Sorry can’t find Campania Express link, do a search on forum, it’s here somewhere!
https://www.sorrentoinsider.com/en/getting-to-sorrento-italy

Thank you all for the great information

Note that the Frecciarossa trains from Rome to Naples are almost 3 times as fast as a road transfer. But their advance-purchase (+- one month advance, but not released until +- 3 months) discounts are non-refundable, non-changeable, for a specific train.

The Circumvesuviana is convenient and very cheap unreserved "subway" like travel. But it can be incredibly crowded and hot in the summer. The problem isn't annoying musicians or apocryphal pickpockets, it's physically getting a real suitcase onto the train and setting it down within sight of your seat or standing area.

There are a lot of durable myths about the Naples rail station, which must go back to GI's re-visiting right after the war! It is a clean, modern, almost-new building with escalators connecting the long-distance area to the lower level. The lower level has the paid rest rooms and the Circumvesuviana, at opposite ends of a VERY long corridor. All that said, we paid for a black car on our return, it was just too jammed on the Circumvesuviana (pre-Covid report.)