Diagnosis
Usually, this is a bandwidth issue, but it's more often the camera's upload speed from your home network, not your phone's download speed. The C510W is streaming a lot of data, and if your home internet upload is slow or congested, the remote feed suffers.
How to Fix It
First, check the stream quality in the app. Tap the HD/SD icon on the live view and try switching to SD (Fluid) mode. This lowers the resolution and bandwidth needed dramatically. Next, rule out your home Wi-Fi: if you have a dual-band router, ensure the camera is on the 2.4GHz band and try to minimize interference from other devices on that channel.
If That Didn't Work
The problem might be the microSD card if you're recording continuously. A slow or failing card can cause the whole system to lag. Try temporarily removing the SD card and see if the live view improves. If it does, replace the card with a high-endurance, Class 10 or U3 card.
Heads Up
Viewing the feed on cellular data will always be more prone to lag than on Wi-Fi. The 'Fluid' mode is specifically designed for these lower-bandwidth scenarios.