Media file (image) does not contain field for title attribute, only for alt attribute.

Plugin add text into title attribute from alt attribute when image is inserted into post if title attribute is empty.

As alternative see plugin 'Restore Image Title' by Les Bessant. The 'Restore Image Title' inserted the post title into title attribute.

1.0

• Initial release

1. Upload 'bg-title-alt' directory to the '/wp-content/plugins/' directory.
2. Activate the plugin through the 'Plugins' menu in WordPress.