Although 16gb should be plenty for most small projects, it could be that you’re genuinely running out of memory.
You could try cooking the project first (File → Cook content for …) and then package (like you would normally do).
Otherwise, you could try optimising the project:
- Remove unused asset
- Resize large textures
- Resize textures to a power of 2.
- Compress any sound assets you have
- Resize baked light maps
- Clean/Retopo any high poly 3d assets
You can also right click your Content folder (in the content browser) and click “Size Map” to check which assets are taking up all the space.