league of legend freeze after 10- 20 min in game and need manually restart.

Do someone have this problem??? My lol work fined but after 10-20 min in game my computer freeze i cant ctrl+alt+del. So i need to hold my power button to restart and rejoin the match. This happen since yesterday and only occur first game of the day. Anyone experience this?? My graphic card are up to dated too. This never happen until i repair my league of legend yesterday. I need someone to help me.