I’m guessing you were selected for some A/B testing of a new feature.
This happened to me too.
Last week, I asked it about some health symptoms, and this week it messaged me asking how I’m feeling and if my symptoms have improved. Freaked me out!
I love how it keeps trying to reach out, almost like it wants to chat but is a bit self-conscious about bothering you. It feels like GPT has a little crush 
This could be really cool and a step toward making it feel less like just a tool. However, it would need to be careful not to do it too often.
An AI bot with enough information to check in on me is also an AI bot with enough data to potentially sell my personal information to unknown entities for tracking purposes. No thanks.