Freezing in mid-game for like 1-3 sec. HELP?

Hey, so I got an issue which ruins all my games and because of that i don't wanna play ranked games. The think is is that my screen freezes in the game at any time for like 1-3 seconds and when it happens in team fights i just die and my teammates flame the hell out of me please help me i cant play league like this because i ruin many peoples game.