Pakis will probably be the first to launch nukes when WWIII kicks off.
It’s far more likely that the Pakistani government will disintegrate, and they’ll lose control over their nuclear weapons. Due to fear the US or India will attempt to take the weapons with a lightning raid, the Pakistanis have taken to shuttling the weapons around in unmarked vans.
Several years ago, the Pakistani army started attacking targets in lands that are nominally Pakistani territory but are not actually under their control. According to an Indian intelligence report this was in an effort to recover a stolen nuclear weapon. The internal (war? police action?) stopped abruptly and I suppose they recovered the weapon. At least I never saw anything on it again and nothing big has blown up. But right now, Pakistan makes North Korea look as stable as the UK.
It’s likely that the first inter-state nuclear conflict will be between two Muslim powers as they hate each other much more than anyone else. Think of the medieval Catholic vs. Protestant wars, but with nukes.