1. Berserks are a myth.
2. In the myth, they are naked or wear plain fur coats, not armor.
I fail to see how a Kuyak makes anyone feel like a berserk.
1. Berserks are most likely, not a myth, from what I've read.
There are numerous references in the more factual saga's, and they are often referenced as the Chieftain's personal guard. From my observation, they seem to possibly be a precursor/earlier version to the later viking age bearded/two-handed axe guards seen among the late viking age, vikings and saxon armies, who where a more organized, uniformly outfitted and more group tactic prepared, personal retinue/body guard of the War leader in question. The extent of these late viking age 'axe guards' are often exaggerated, such as the Jomsvikings etc, but it is pretty well accepted, that the Saxon army of Harold Godwinson, probably had the finest example of these 'axe guards'. Its also of note, that, 1066/hastings seems to be the high point of the 'axe guard' and from this point on, they became secondary and then all together gone, replaced by heavier Cavalry, heavier armor, and longer polearms, and battle tactics that no longer could use them effectively. Atleast in the west. Its likely that the bearded axe continued on as an infantry weapon, but as a trained broup, and bodyguard, they seemed to fade into history.
2. They are also not always referenced as purely naked or in furs. They where as referenced, more likely to go into battle less armored, and to cast away thier shields and helmets etc, at the proper time, in order not to exhaust themselves more.
3. There are references (I believe by the romans) of Continental Germanics from an earlier age, related to the Vikings, belonging to an Odinic/Wotanic cult, that, painted themselves black, and went into battle in such a way, but, the references in the later saga's, do not refer to berserks uniformly going into battle unclothed/in furs only, or even lightly armored, in some cases. You may have seen an example of these earlier Wotanic berserkers in TW barbarian invasion, and Europa barborum.