The phrase "at a suddenly" is not correct and not usable in written English.
The correct expression would typically be "suddenly" on its own or in a different construction.
Example: "At that moment, everything changed suddenly."
Alternatives: "all of a sudden" or "unexpectedly".
Though I welcomed the prospect of hanging out at a suddenly erstwhile nude beach and gawking at the novelty of the situation, Tom Cooper was dismayed.
Unbelievable!" was Thorne's call of the eighth-inning homer, sealing Baltimore's 10-6 win over the Yankees and locking the teams into a first-place tie as this weekend's four-game showdown opened at a suddenly boisterous Camden Yards.
Lebanon's hothouse politics have been thrown into turmoil by Syria's insistence -- at a suddenly summoned special cabinet meeting over the weekend -- that the president it chose for Lebanon stay in office past his constitutional term.
Gazing up at a suddenly towering figure, or rushing excitedly down a corridor toward a door that has just slammed shut — almost pruriently interested in what is going on behind it — the camera becomes a seemingly subjective intelligence, part of the story that it tells.
As Kate and Thor depart by hammer on a mission to thwart the Draycotts' evil plans, Dirk watches the sinister Simon and Cynthia arrive at a suddenly deserted St Pancras.
But this is what they were reduced to: As they stood on those chairs, atop soft, white-padded seats, exhausting their lungs to scream questions at a suddenly reticent presidential candidate ― Will you apologize to President Obama?
In large ways and small, and now at a suddenly-accelerating pace (today gay marriage, tomorrow marijuana legalization, etc)., we're getting the culture that social liberalism wants — less traditionally religious and more socially permissive, with fewer normative ideas about how sex and love and childbearing fit together.
Tonight it's ladder-leading Freo at home to a suddenly buoyant Richmond.
She hasn't lost a Grand Slam match since 2014 at Wimbledon, when a suddenly overachieving French woman named Alize Cornet frustrated her with drop shots and won.
He grabbed at her, and kissed her kissed and bit at her lips, like a suddenly ravenous rodent.
He grabbed at her, and kissed her — kissed and bit at her lips, like a suddenly ravenous rodent.
