My first thought is that your neck is simply not used to holding your head stuck out horizontally , especially with 3/4 of pound of helmet strapped to it. Some simple exercises might work wonders. I don't have suggestions, but I'll guess a Google search will turn up something.

I have never gotten very far from riding my road bikes, but just being off them for a couple of months means that I will feel my neck after rides. I understand you have never ridden them. If my neck were in your shoes it would be telling me "what are you doing to me? I have to spend the next half hour holding this weight at arms length?" But with exercise, it will get used to the idea and by spring, you won't even think about it.

Ben