By default, or originally it is usually aligned to the the left.
Centralize Sidebar Title Blogger
Here is what you need to do centralize the title of sidebar widget for Blogger.
1. Go to Blogger Dashboard.
2. Click "Theme".
3. Scroll down the slider until "Advanced".
4. Click on "Add CSS".
7. A box will appear on the right hand side.
8. Paste the code below in the box provided.
.section-columns h2, #sidebar-right-1 h2, #sidebar-left-1 {text-align: center;}
9. Click on the orange color "Apply to Blog" button.Now you should be able to see the all the titles of both sidebars widgets of your Blogger blog aligned to the middle.