Over soon.

During a somnambulism attack, he leaves Zhou Palace in the middle of the night, sleep-walking to some unknown destination.

He appears back only three days later, under the effect of some deep sickness.
Although vomiting even without eating, crying blood and being affected by tremendous pain, he refuses to call any doctor.

He soon falls unconscious.
If any doctor was summoned, he wouldn't be able to tell the causes nor a possible therapy.
There is no track of poison in his body, nor wounds or other traumas that could cause such a violent response from his body.

Before falling unconscious, QinShi was certain to die. But for once, he was wrong.