Hey there,
The reason why Eliezer has strong reaction to hearing the Kaddish at the moment is basically because he was the one who rebelled against his religion, and from this he always thought why would God (which is loving) do something like this. Elie then doesn't pray to God to help him in the case that he need's help with.
Final answer:
![\boxed{Because \ he \ is \ so \ afraid \ of \ dying, \ the \ prayer \ terrifies \ him \ and \ makes \ him \ think \ that \ his \ own \ death \ is \ imminent.}]()
~Jurgen