Is it normal to give my wife a haircut during sex

What's an erotic haircut? Are you going to shave a cock symbol into her hair?

have you really thought through how this will play out?

you're thrusting while snipping at her head with scissors?

are you sure you want to do that?

Before pitching the idea to the mrs consider how this will work. And maybe go watch that Alan Rickman movie where he plays a hairdresser. that might give you some ideas on how to make it erotic (it's called "Blow Dry")

There are plenty of Hair-fetish people all over the world (even if they don't know they are hair/haircut-fetish). There will be urges you have when you see long beautiful hair or more when you have seen such videos where ladies get short hair cut or get their head shaved.

Absolutely normal. You didn't even need to ask the question.