Here is what we recommend if you experience this issue often:
1) Use Wi-Fi connection instead of 3G or 4G.
2) Avoid playing the game while traveling. Your mobile device will constantly switch base stations even on a short trip. This might cause screen lag or total loss of connection.
3) Terminate or shut down other applications which might be running in the background of your mobile device. Each application running in the background will surely use memory and CPU. Depending on type of these applications, this might adversely affect the performance.
4) Try to keep the battery charge of your mobile device above 50%. If the battery charge drops below a certain level, your device will probably switch to power saving settings. These settings could decrease the performance of your device as well.