No power to radio or nav screen

The problem started with the headlights going out, the AC blowing warm air while I was driving. When I stopped the car and tried to restart it starts for two seconds and then goes off.

list the maintenance and repairs that are suggested

After new battery, stop for two weeks and started again. First time it went off it was off and on for two day.

what are the B1 B2 ect? services? 95,000 miles