Thank you for your replay.
As per your link, I checked…
1. Hosting issue: Currently I am using Bluehost where there is not such kind of issue of limited quota / server has down.
2. No, my site hasn’t been hacked. It is working perfectly but database connection issue come suddenly, especially when add/update new post. This is the result of my scan : https://sitecheck.sucuri.net/results/www.sclrship.com/
3. Auto Upgrade is working perfectly. Nothing wrong with that.
4. Even I checked with a default plugins and theme of wordpress, but same things happened.
