It could be that a Windows update is causing your problem. Do you know if one occurred at the time your problem appeared? If so, try rolling back to the previous version.
Another possibility is that your graphics card or your computer is failing. One quick check to see if the problem is being caused by your graphics card is to check "Use software OpenGL" under Tools/Options/System Options/Performance. (You have to close out all of your assemblies, drawings and parts before you can change this setting.) If the problem goes away, then the problem is in your graphics card or your driver.
Your graphics card is not approved by SolidWorks. One fairly inexpensive fix would be to buy a low to mid-range graphics card, such as the AMD FirePro V4900 and install the approved driver from the SolidWorks website.