USB-C ports have a flaw in their physical design. Due to the shape of the port, dust and other gunk slowly gets jammed down into the port and eventually enough builds up that you can't get a good connection anymore. It happens after about two years for me and has happened on every USB-C phone I've had.

It's pretty easy to clean. I'll turn off my device, fill the port with rubbing alcohol, and scrub around with a pin of some kind. It takes me about 10 minute and you have to be kind of aggressive with it. I find that by the time I start having issues, the quantity of gunk I remove is about the size of a grain of rice.

Here is a short video on it: https://www.youtube.com/watch?v=GIoTlY1Wm4Q