it only does that to me on my recovery days. kinda annoying, I run 6 days a week and on the 1 day I don't I get yelled at by my watch about it.
pretty sure it has to do with your step tracking, if you haven't walked much and you usually do by a certain point, it says something is off. I run in the morning, so usually hit my 10k steps by 9am, so on non run days, around 9-10 am I get the "something is off" message.
The message may come from Insights... In Garmin Connect Mobile, at the bottom of the screen, select More (...) and then Insights. You may have a few messages there and you can select the 3 vertical dots at the top right of the screen to unsubscribe to Insights if that is what you want.
I think Insights, is Garmin's way to try to encourage us to move more.