Many users have been experiencing performance issues in multiple version of Civil 3D (slowness, lag, temporary freezing, etc.). This has been happening even on machines that have plenty of RAM and processing power, and it can be very frustrating. Well, it took a few years, but it looks like AutoCAD has found a way to help. So, they created an update! Click here to to get a ZIP file and separate instructions for applying the update to each of the versions of Civil 3D listed above (2014, 2015, 2016, and 2017).
Make sure you follow the instructions that apply to the version you are using. Hopefully, this solution will work for you and your team can get back up to full speed ahead!