2002 325i Alternator Issue

I've read through some other posts here on alternator issues, and I've received a lot of great info, but I'm having one variant to a possible alternator issue I hope someone can help me with:

Started car this morning and the alternator charge warning lamp came on. It stayed on for a minute or so and then went off. I drove about 4 blocks and when coming to a stop sign, the car died. It started right back up and I had no more problems with stalling (drove a few miles and came home).

Ran diagnostics for both battery and alternator charge and battery was showing 12v with key 'On', and when I started the car, I saw no movement from 12v to the 14v I expected.

A couple of hours later, I ran the diagnostics again, and when I started the car, this time, it jumped up to the 14v, and seemed to be running fine.

I don't think this is an alternator issue, but more of a voltage regulator issue. Would like to know if anyone else has ever experienced this kind of system charge inconsistency.

Forgot to mention the battery is brand new.

Why was your battery changed?