Around what year did signs of the decline of the roman empire begin to appear

You could say the years after augustus. the Catholic church in someways strenthened but weakened the empire after its legalization in 315. The hired barbarian mercenaries became Rome's military. the west fell but the east stayed one of the strongest empires in the world for a while. 800 is when Charlemagne was crowned emporer of the roman empire so the roman empire kept on dying and coming back like the Carolingian renaissance and the Renaissance. Renaissance comes from the French re birth. its a broad question