DIAGNOSIS The Wi-Fi module in the C3 (and many smart TVs) can be weak, especially on congested 5GHz networks. Streaming 4K requires a stable, high-bandwidth connection, and dropouts happen when the signal fluctuates.
FIX Try switching the TV's Wi-Fi band. Go to Settings > All Settings > Connection > Wi-Fi Connection > (your network) > Manage Settings. Change the 'Frequency Band' from 'Auto' to either 2.4GHz or 5GHz explicitly. 2.4GHz has longer range and better wall penetration, which might be more stable even if slower. If you have many other 5GHz devices, forcing the TV to 2.4GHz can help.
IF THAT DIDN'T WORK The best solution is to use a wired Ethernet connection. The C3 has a 100Mbps Ethernet port. While that's slower than modern Wi-Fi theoretically, it's often more rock-solid stable for streaming 4K, which rarely exceeds 25Mbps. If running a cable isn't possible, consider a powerline Ethernet adapter or a dedicated Wi-Fi extender with an Ethernet port placed near the TV.
HEADS UP Don't just keep reconnecting. If the Wi-Fi module in the TV is faulty (less common, but possible), constant reconnection attempts can overheat it. If wired Ethernet works perfectly, you've isolated the problem to the TV's wireless hardware, and you might want to just stick with wired.