When I lived in Torino there was "bike-sharing." There are racks of bikes all over, owned by the city. It was automated. You could pick up a bike, pedal to where you wanted to go, and usually there would be a city bike-sharing stop nearby where you could drop off and lock up the bike. You often used one to carry your groceries home. The city would charge you by the minute. The goal was to reduce air pollution. Milan, a city with horrific air pollution, has bike sharing too, and it's very popular there.

Rome is not quite as polluted as Milan, but it started bike sharing a few years ago for the same reasons. The only problem was, within a few months Romans had stolen most of the bikes, so the city gave up on the idea.

In Spain there's a company called Cooltra. They rent Vespa-like scooters, using the same format as bike-sharing. They recently opened in Rome. They'll even deliver the scooter to your hotel if you're not near a stop. They have a pick-up/drop-off point at Termini. I don't think they have that many spots yet, but for example, you can go to Termini, rent a scooter (comes with 2 helmets) and drive to the beach instead of taking a taxi. You handle it all with the eCooltra app on your phone.

They're electric "vespas," with zero emissions. Although it's a private company, Rome is hoping that this becomes popular, and that citizens will use them to get around, thus reducing pollution.

After having two serious motorcycle wrecks in my younger years, although those were on monster bikes, I'm not encouraging anyone to rent a scooter in Rome. But if it suits your fancy to have that Gregory Peck/Audrey Hepburn experience, it's at https://www.cooltra.com/en.

If you do this, unless you have lots of driving experience in Rome, I'd suggest heading outside of the city center and not towards it.