The Golden Age, also known as the First Golden Age of Cybertron, was a period in Transformer history on their homeworld of Cybertron when their world was rich in energy and the inhabitants were at peace with one another. It ended with the beginning of the Great War.
The Transformers cartoon
Nine million years ago, Cybertron was at peace until Megatron led his newly formed Decepticon army against the peaceful Autobots which began the very, very, very long series of wars that resulted in a broken planet.
Cybertron entered into a new Golden Age when the Plasma Energy Chamber was used to repower the planet which was now in the hands of the peaceful Autobots, who would probably use it a lot better than the Decepticons did....