This morning I tried to log in to my Gmail account only to discover it was locked due to "unusual activity detected".
It gave me the option to verify my account via phone, which I did, and I got control of the account again.
After looking up what could trigger unusual activity, I learned I can see the details of the most recent activity on my account via IP addresses that have logged in. All of the addresses belong to me and nothing is out of the ordinary at all in the last 2 days. They only locked it this morning, because only a 4 hours earlier I accessed it just fine.
Does this mean perhaps someone had several failed entries trying to invade my account? Has anyone else had this issue before?