You can stop a render at any point or let it end by reaching the rendering limit (pass, noise, or time). Then, you can resume rendering from that point later. You can find the two available options for resuming rendering under the vertical arrow next to the "Render" button:
This can also be done in the Cinema 4D native picture viewer under the Corona drop-down menu:
Resume Last
The Resume Last command allows you to continue the most recent render from the point at which it was stopped. This is possible as long as the image has not been cleared from the Virtual Frame Buffer (VFB).
When resumed, the renderer builds upon the previously completed render passes. This applies whether the process was stopped manually or by reaching a render limit.
For example, if a scene had completed 10 passes and you resume with a Pass Limit of 10, the renderer will execute another 10 passes. The final render will have a total of 20 passes. If resuming with a Noise Limit, rendering will continue until that target is reached. If the stopped render was already below the target noise level, the render will stop after one additional pass.
Resume File
If you would like to resume rendering at a later time, you can save the CXR file, and then use the "Resume File" option.
See: How to save .CXR files in Corona for C4D
Corona's EXR format (CXR) is an EXR file that includes additional data allowing a render to be resumed from its saved state. When a CXR file is used, the rendering process follows the same principles as the "Resume Last" option, continuing until the render limits defined in the Render Settings are met.
Again, this can also be done in Cinema 4D's picture viewer under the Corona drop-down menu by selecting Dump to CXR:
Note: for the "Resume Last" and "Resume File" options to function correctly, the scene currently loaded in Cinema 4D must be identical to the one used for the original rendering.