Game sometimes won't load

Sometimes after champ select, the client disappears and doesn't go into the loading screen. Sometimes it works perfectly fine... but it's increasingly getting worse and worse. Once in a while, it also freezes at 100%. All I can do is go into task manager and close all league processes and restart. Upon restart, it always works. However, by the time I'm finished loading, it's anywhere from 1 minute to 2 minutes and 40 seconds into the game. I've lost 3 games because of this and stopped my rank climbing today... very annoying. What could be the cause?