"at its beginning" is correct and usable in written English.
You can use it when describing the start of something. For example: We recognized the song at its beginning.
A decade into its run, the restaurant remains comfortably modern in tone, perhaps even more so than it was at its beginning.
Humpty Dumpty may well be rather different at the end of its run, in late January, than it is at its beginning.
The chief interest of European lacquer of the 18th century lies, however, in the fact that it was not a purely imitative art, as it had been at its beginning.
Nevertheless, Mr. Heins predicted that RIM would still hold more cash at the end of its fiscal year than the $2.1 billion it had on hand at its beginning.
Most people were worse off near the end of the 16th century than at its beginning.
At its beginning the Italian kingdom was still a powerful and coherent institution, worth fighting civil wars to control.
It was as if, for Holbrooke, the year would always be 1962, his career at its beginning.
With many onlookers in silent admiration for the past hour, it's a fitting ending to a band cutting their teeth on new material which will hopefully mean they end this year less invisible than at its beginning.
But as the winter snow begins to fall, American and NATO forces have reached the end of the fighting season without suffering the big reverses they feared at its beginning.
The development of nanoagents to improve the performance of particle therapy is only at its beginning.
Modern Long Term Agricultural experiments (LTAE) have a long history initiated when modern agricultural science was just at its beginning.
