terminology

This sort of behavior is quite literally called shivering thermogenesis so yeah this is more appropriate wording.

Also rewrites the moodlet to be more fitting.

nsv13/code/datums/mood_events/nsv_events.dm

@@ -53,6 +53,6 @@
 	mood_change = 3
 	timeout = 30 SECONDS
 
-/datum/mood_event/lizard_vibrations
-	description = "<span class='warning'>I know my muscles are shaking to warm me up, but it still feels distracting..</span>\n"
+/datum/mood_event/lizard_shivers
+	description = "<span class='warning'>I'm shivering.. I need to find a spot where I can bask in the sun!</span>\n" //Evolved mental response, even if not entirely true here.
 	mood_change = -2

nsv13/code/modules/mob/living/carbon/human/species_types/nsv_lizardpeople.dm

@@ -26,18 +26,18 @@
 	if(cold_stacks < LIZARD_THERMOGENESIS_COLD_TRIGGER_STACKS && !fibrillating)
 		return ECTOTHERM_NO_THERMOGENESIS_NEEDED
 	if(!fibrillating) // !fibrillating reaching this point means enough stacks exist.
-		to_chat(human_holder, "<span class='warning'>Various muscles across your body start quivering!</span>")
-		SEND_SIGNAL(human_holder, COMSIG_ADD_MOOD_EVENT, "lizard_trembles", /datum/mood_event/lizard_vibrations)
+		to_chat(human_holder, "<span class='warning'>You start shivering and feel the urge to find a sunny spot!</span>")
+		SEND_SIGNAL(human_holder, COMSIG_ADD_MOOD_EVENT, "lizard_shivers", /datum/mood_event/lizard_shivers)
 		fibrillating = TRUE
 	else if(cold_stacks == 0) //We also check if we have to stop vibrating here.
-		to_chat(human_holder, "<span class='notice'>Your muscles calm down.</span>")
-		SEND_SIGNAL(human_holder, COMSIG_CLEAR_MOOD_EVENT, "lizard_trembles")
+		to_chat(human_holder, "<span class='notice'>You stop shivering.</span>")
+		SEND_SIGNAL(human_holder, COMSIG_CLEAR_MOOD_EVENT, "lizard_shivers")
 		fibrillating = FALSE
 		return ECTOTHERM_NO_THERMOGENESIS_NEEDED
 
 	return ..(human_holder, FALSE) //We already use some fancy logic for our thermoregulation triggering so we don't use the normal temp difference check save for if we would get hot.
 
 //Modular proc attachment
 /datum/species/lizard/on_species_loss(mob/living/carbon/human/C, datum/species/new_species, pref_load) //Human variable, named C. What did they mean by this?
-	SEND_SIGNAL(C, COMSIG_CLEAR_MOOD_EVENT, "lizard_trembles") //Safely remove if our species is changed.
+	SEND_SIGNAL(C, COMSIG_CLEAR_MOOD_EVENT, "lizard_shivers") //Safely remove if our species is changed.
 	return ..()