Lag in game when the pc has been running for some time.

Since the patch you got after preseason patch i've gotten this FPS-Drop problem in game.

When i turn the computer on and enter a game it's all fine throughout the whole game, But I usually take breaks between games and that's when everything gets laggy. After a break, which usually includes just using my browser, I enter the game and i get Fps drops from the start I'll have 250 fps for one second and then it drops to 15 and then it goes back up to 250 and then back down It does this constantly which makes the game unplayable.

I've tried different solutions: Closing browser (evem though it was never a problem before.) Changing settings to lower settings(even though it havn't been a problem before and i have an okay computer) Tabbing in and out of the game which usually solved lag back in the days. doesn't work anymore unfortunately..

My only solution right now is restarting my pc before games, which i forget sometimes and then i gets problematic cuz leaving mid game is quite devastating.

Anyone else that has this problem? Anyone who solved it?