、。
Kei flinched at the question, but shook his head as if to say it was nothing.
Literal
Kei [topic-は] that question [at-に] got-startled [was-させられた], but head [object-を] nothing is [quotative-と] wanted-to-say-seemingly [manner-に] shakes horizontally.
A narrative beat from fiction. ギクリ is a 擬態語 (state mimetic) for a sudden startle — the internal 'jolt' feeling when you're caught off-guard. ギクリとする = 'to flinch,' 'to feel a jolt of surprise/guilt.' Here it's in the causative-passive form させられる: 'was made to feel a jolt' — the passive of the causative, meaning 'was involuntarily flinched by X.' This compound pattern reflects being affected by something you couldn't control. 何でもないと言いたそう uses ~そう (appearance) on 言いたい ('want to say') to give 'as if wanting to say it's nothing.' 横に振る ('shake side to side') is the gesture for 'no.'