Control Panel\All Control Panel Items\Ease of Access Center\Set up Sticky Keys, uncheck "Turn on Sticky Keys"
Other suggestions;
Make sure you have the most current drivers available for your keyboard and mouse.
Make sure that you have no unusual mouse button assignments that would correspond to a key on your keyboard.
Also include as much detail as possible about your PC and the hardware causing the issue. Manufacturer, model name, model number, etc. Often times members will have specific information based on experience with similar hardware.
And welcome to the forums.