How do you write the sound of a shudder?

Answer 1

There are two onomatopoeias I favor for this:

The more traditional one, for shivering (as in because of cold), something like "brrr" where the 'r's can continue indefinitely.

For a shuddering (as in because of disgust or creepiness), the best I've come up with was "guhuhuh" where 'uh' can continue indefinitely. I've also seen "ugh", 'yick", and various related words used instead.

Answer 2

You could write the sound of a shudder as "shiver," "quiver," or "tremble." These words capture the trembling or vibrating sensation typically associated with a shudder.