What did Winston wake up shouting and why did it terrify him?

Winston woke up shouting "Julia!" in a moment of panic that terrified him because it revealed the depth of his feelings and connection to her, which was dangerous in the oppressive regime of the Party. His subconscious fear of being discovered for his rebellious emotions and thoughts about love made this realization particularly unsettling. It highlighted the constant threat of surveillance and the potential consequences of expressing forbidden desires in a totalitarian society.