Mouse sesitivity bug

When ever I get into a game within the first few seconds my mouse sensitivity increase to a point where I cant play. To try and fix it I lower my sensitivity in game and in my mouse settings. When I do this it goes normal for a second or two but then it goes back to being really high. I have tried restoring all setting to default and re installing the game, I ever bought a brand new mouse. Nothing seems to be working please fix this bug. Also please let me know if anyone has the same problem or solution it would be much appreciated. This bug is really starting to get on my nerves and make me not want to play the game.