I have had this happen quite a few times. It can be a bit unsettling. On a few occasions it was a booming voice in my head warning me. And then over the past year I've had a half dozen times when I am alone at home and I hear a voice call out my name that will sound exactly like my Dad, wife, or son. Something is mimicking their voices. It's very unsettling. I personally don't know the meaning of what that was all about.
I have had what I believe to be ghosts whispers in my ear on occasion while I sleep. That could be the case for you. But then you did hear a voice again when you started waking up. It could be an angel. It's always tough to tell. Did anything else happen during that time that made the atmosphere in the room feel different? Or did you have ringing in your ears or sounds?
Interesting. One of my goals this year to find a better way to separate ghost interactions from ghost interactions. I usually can't tell which is which. But for me when something paranormal happens I usually get a strong feeling that the atmosphere in the room has changed. It's hard to explain but everything feels and seems different eventhough I can't pinpoint what it is. I also usually will have either my left or ear ring pretty strongly.
I read once that ghosts often carry emotions that they took to the grave (unhappiness, regret etc...). And when they interact with us empaths we can often feel that emotion. Whereas with angels, there is usually a calming feeling that they project on you.
It sounds like since you were calm that you most likely had an angel encounter. And I think the fact that it came as a voice in your head that no one else in the room heard is another tip off. And it would seem that by being woken up that you avoided getting in trouble with your manager. There is probably an important connection there.