shiver vs instinctive reflex

shiver and instinctive reflex both are nouns.

Word	Noun	Adjective	Verb	Adverb
shiver	Yes	No	Yes	No
instinctive reflex	Yes	No	No	No

As nouns, instinctive reflex is a hypernym of shiver; that is, instinctive reflex is a word with a broader meaning than shiver:

shiver: a reflex motion caused by cold or fear or excitement
instinctive reflex: an automatic instinctive unlearned reaction to a stimulus

shiver (noun)	instinctive reflex (noun)
a reflex motion caused by cold or fear or excitement	an automatic instinctive unlearned reaction to a stimulus
an almost pleasurable sensation of fright

shiver (verb)	instinctive reflex (verb)
shake, as from cold
tremble convulsively, as from fear or excitement