Depending on the 5G coverage in your area, sometimes the best thing is to turn 5G off altogether and stay on 4G, as 5G is a major battery drainer, especially in the areas with poor coverage.
5G is designed to work best in crowded places (airports, stadiums, concert happy and such), but in rural areas, at least for now, you may not get good speed benefits vs 4G and will definitely get a poorer battery life.
If you want/need it on 5G, just put it on Auto and it will use it whenever there is a good 5G signal.