My symptom, too: at about the same time a few days ago I started getting messages that memory is low, even though the phone is only about 40% full, and the battery life when gonzo. Also some weird things started happening in some apps, like clicking a notification in Facebook would launch Edge instead of going to the post in Facebook.
I thought the storage space message was maybe related to me putting a 128GB SD card in, and maybe the percentage of phone disk was skewed by that, but from these posts it seems like it is more generic.
Last night it would not even recharge after a night on the wireless charge pad. So I am doing a reset as I type. I'll post the results.