「寝てた？」「爆睡」「そ、そうか？」「なんかうなされてたよ。怖い夢でも見てた？」

「？」「」「？」「。？」

'Were you sleeping?' 'Dead asleep.' 'O-oh, really?' 'You were groaning. Were you having a scary dream or something?'

Literal

'Was-sleeping?' 'Deep-sleep.' 'I-is that so?' 'Somehow was-being-groaned. Scary dream [or-something-でも] was-seeing?'

Natural rapid-fire dialogue. 爆睡 (dead/explosive sleep) is casual slang for sleeping very deeply. うなされる is the passive/spontaneous form of うなす — 'to groan in one's sleep,' something that happens to you. ~てた is the casual contraction of ~ていた. The stammered そ、そうか shows surprise. ~でも (or something) softens the question.