Scrolling and Clicking Sometimes May Not Work

This could be a bug produced from my computer but after a couple days from it, it seems to come from the game itself. When I want to scroll to my desired item, or break/place/hit a block or person, the scrolling does not work temporarily and when I click, my cursor appears outside the game's box but the outline of Minecraft is grey indicating that I am not currently able to play as if I minimized Minecraft. But however, I can still play it by simply clicking into it and playing it again with NO problems (the scrolling and clicking is fine) until no more than five minutes of non-intense activity in Minecraft, the bug appears again. When I am in an intenst activity it will take about ten minutes for the bug to appear again.