Is it normal to get aroused by women's neck?

Its the best spot to suck the blood from your victim.

You have both carotid arteries right there to drain the vitality from the sheep and perpetuate your vampiric being further thru the annuals of history

Weird but fine.

The body of your partner, in an ideal stance, is a wonderland of attraction. Your gaze has shifted beyond the typical sexual characteristics and into the land of looking for more in the totality of their physical form.
Even if you don't feel 'normal' - consider that you have a wider angle sensual gaze when you look upon that which you desire.

My old man was never attracted to necks till he met me.