Travel from rome to sorrento

The bus service I would recommend only has service leaving Rome at 8 am
https://global.flixbus.com/

If you need to leave at 3 pm take the fast train from Rome to Naples in 1 hour.
At Naples walks down stairs and catch either the Circumvesuviana (this is the least expensive and has a bad reputation among the tourist bourgeoisie) or the Campania Express http://ots.eavsrl.it/web/public/ots/ticket/index?changeLang=en to Sorrento.

Taking the train and arriving at Sorrento in the evening is safe I do not know where you got the idea that it is not.
I went last May from Rome on the trains described above, arrived at 8 pm and did not see or feel anyone looking to strong arm rob or mug tourists.

You should and most would recommend you get a recent guide book.

Yep, what Jazz+Travels said.

Nothing wrong with the Circumvesuviana train. I'd take it even at night without worry. Sorrento at night is delightful.

Auto Club has never been anywhere near Sorrento and is just reading from a script.

I don't how you determined that it was not safe but you are arrival very later afternoon to early evening and it probably would still be light so I would take the train since bus service doesn't run that late.

As said above: your best solution is to take the Circumvesuviana from Naples to Sorrento. It's a battered, no-frills thing but gets the job done and is how many locals in that region get around too.

Alternately, if you were willing to leave Rome Termini at 13:53 (1:53) instead of 3:00, you would get into Napoli Centrale at 15:03 (1 hr, 10 minutes) and could take the 15:39 Campania Express to Sorrento, arriving at 16:25. It's a slightly more expensive train but it's also a little nicer and makes fewer stops on the run to Sorrento.

https://www.sorrentoinsider.com/en/campania-express-train-schedule

Napoli P. Garibaldi station - where you'd pick up either the Express or Circumvesuviana - is connected to Centrale.
Sunset isn't until 7:00 (19:00) so whichever train you use from Naples, you can get there before dark, not that traveling at night is unsafe.

The Marozzi bus leaves Tiburtina station at 3:00. It is a direct bus to Sorrento. It makes one bathroom break stop along the way and a few very brief stops in towns closer to Sorrento. It is a four hour ride, your luggage goes below. It will drop you off in Sorrento on Corso Italia near the train station. You can buy the tickets online but I've always bought them on the day of travel at the Tiburtina bus station. Here is a link: https://www.marozzivt.it/home.
Buon viaggio.