Most of central Rome is a ZTL (Zona a Traffico Limitato) — restricted traffic zone. Cameras fine non-residents 100+€.
Park outside the ZTL and take public transit in. Parking garages near Termini, Tiburtina, and Trastevere.
Uber operates but is rare. Taxi from main ranks (Termini, Trastevere) is the easiest non-public-transit option.