Adobe Illustrator doesn't have any built-in object nesting functions. There are nesting plugins for Illustrator that cost varying amounts of money (usually on an annual basis). Certain kinds of industry specific software, such as some large format RIP applications and routing applications can automatically nest objects into a defined material size.
Deepnest.io is an open source stand-alone application that can nest vector objects. It doesn't work with native AI files, but can import SVG, DXF and Corel CDR files. It can export DXF and SVG files.