I 'shudder' at the thought of what might happen. = 'I shudder to think' (of) what might happen. [=I am very worried/fearful about what might happen]
He 'shuddered' [='quivered, trembled'] 'with' fear when he heard the scream.
I felt a 'shudder' [='tremble'] in the floor as the truck drove by.
(..) We were afraid it was somebody important. Yeah, you know, like Mufasa. Yeah. I see. Now that's power. Tell me about it. I just hear that name and I shudder. Mufasa. Ooooh.... Do it again. Mufasa. Ooooh. Mufasa. Mufasa! Mufasa! Oooh! It tingles me. I'm surrounded by idiots. (..)1994 The Lion King