This was the most bizarre of the things I was experiencing that I found was related to PTSD. I asked about this soon after joining here and many people confessed to experiencing it. I had noticed this years before my PTSD diagnosis. It is not something you are "doing" consciously, and even when you're aware of it, it is hard to "fix".
I have learned to work around it as much as possible. If my husband is with me, he will whisper that someone we know is approaching us in a store, etc. and will tell me their name, and how I know them and any important details (new baby, house, etc.) We have always insisted that people call before stopping by and then I always focus on their vehicle, height, hair color, things I can remember. I do not experience this with women, so if they are with their spouse, I can deduct the identity of the man by recognizing the woman.
Ironically, I have no problems with still photos, video, etc. Social media has helped because I can look someone up on Facebook and "see" them and then get a picture in my brain that I can pull up when I meet them, although I still can't match them directly. It does seem to get better with frequent repetition. I can now recognize our male postal carrier and the repeat drivers for Fed Ex and UPS. Although, I'm not sure if I would recognize them on the street.
So, you are not weird, it is just another symptom that you have to deal with and work around. This was really scary for me too. Since I didn't even know I had PTSD, I was looking for all kinds of physical causes. I even had a MRI to rule out brain injury or tumor, etc. I can't say if it will subside, although I hope so, but you can work around it with a little creativity.
