This is from the Fair Play Policy (Help & Support, down by the green pawn.
On his or her turn, each player has 15-20 seconds to make their first move. If this does not happen, the game will be automatically aborted. This has a negative effect on the Fair-Play record of the player failing to move. (But if you hit Abort, it affects your record! It's best to be patient for a few seconds.)
Auto abort what is it. And why does it come up only some times?