My database keeps stopping

Summary:

I am using Always Free tier Autonomous Database. It stops continuously.

Content (required):

I think that same question is below. I have the problem that my ADB keeps stopping.

My database suddenly stopped 3 days ago. I started it manually, but it stopped again.

I checked that storage utilization is 23% and sent dummy queries but no use.

I want to know what the problem is and how to fix it

Version (include the version you are using, if applicable):

19c

Code Snippet (add any code snippets that support your topic, if applicable):