My sister and I will travel to Florence and want to spend 4 days on coast in nice hotel with access to sandy beach before traveling to Rome. We will not have car and depend on train. We will travel next May. Any recommendations for town and hotels will be greatly appreciated.
Consider Orbetello. Mid way between Florence and Rome.
https://www.visittuscany.com/en/ideas/10-things-to-do-in-orbetello/
I'll just chime in to say take a look at San Vincenzo if you are looking for hotels along the beach. The rail line comes into town with the station just blocks from the water front. Other locations the rail line is about a mile or so from the beach requiring a taxi, not that a taxi might not be needed in San Vincenzo to get to your hotel. Look on google maps to find beach front hotels.
https://www.visittuscany.com/en/towns-and-villages/san-vincenzo/
From Orbetello you can take a bus to the old town (some great sandy beaches reachable on bike from here--google Feniglia), or further along to the rocky promontory where there are two tiny towns, Porto Santo Stefano and Porto Ercole. It would be difficult but not impossible to get to some beaches from those spots, if you like rocky, dramatic beaches--or take a ferry to Giglio. The train line then moves inland until the second good suggestion, San Vicenzo.
What part of May? Sea does not rally begin to warm up until late May.
Keep on mind that Rome is at the same latitude as NYC.
Starting from Livorno, going south, the nicest places easily accessible by train are:
Castiglioncello
Rosignano (Spiagge Bianche=white beaches)
San Vincenzo
Follonica
Santa Marinella
There are others but you would need a bus.
Do a Google Image search to see which you’d prefer.