Those dismembered dolls, especially how they appear in brief snippets without explanation... and Mei's insinuation that the dolls are trying to suck out your soul doesn't help.
In Episode 3, things go from zero to 60 in about three seconds. To wit, Yukari Sakuragi sees Mei in the hall, panics, and flees down the stairs, whereupon she trips and gets Impaled with Extreme Prejudice on her umbrella. And it's shown in graphic detail.
Then there's Episode 4... Not only does it recap Sakuragi's death in the Cold Open, Mizuno is killed in a malfunctioning elevator. They don't show her face being crushed in as she falls down once, but three times!
Takako popping up behind Kouichi and saying "It wasn't me" calmly is also an extremely creepy Jump Scare
Teshigawara and Mochizuki opening one of the hotel room doors to find the insane, blood spattered, knife-wielding old lady who lives in the house, who then proceeds to try and stab them. Then there's the later Jump Scare when they try to enter the fire exit, only to find a dead body already in there, staring at them wide eyed.