The C reactive protein itself doesn't cause symptoms on its own. It's produced by the liver in response to signals from immune cells. It actually binds to bacteria in circulation, so if anything it helps. As a data point, it can vary by >1000x during the course of a disease, and won't be something that people feel or complain about separate from the other symptoms.

The underlying cause of the inflammation usually does produce other symptoms though. Think fatigue, joints, stuff like that. It's one of the many biomarkers that can alert people to change their lifestyle and diet. When they do, they usually feel much better and there will be a reduction in inflammatory markers coincidental with them feeling better.