99 9-5 Saab wagon starts but wont start again?

itll start up once but after i drive it around it wont start again, i can hear the clicking from the starter solenoid, but it wont start again, and once the engine started and then cut back off, the battery is good i took it up to the store, but now im stuck and i dont know what to do any suggestions?! Please help i really appreciate it.