There could be many reasons for this.
Was SolidWorks working okay previously and now all of a sudden it's just started happening? Or is this a new install?
Does you computer and hardware meet all of the recommended SolidWorks requirements?
What are your computer, OS, and graphics card specs?
I bet on the graphic card drivers.
If you check the Use software OpenGL in the performances in system options.
Then make another sketch, it should work.
If that's the case, you need to update the drivers with one certified by SolidWorks : Graphics Card Drivers | Hardware & System Requirements | SOLIDWORKS
Edit : link in English, not in baguette.
There can be many issues. Make sure one by one it is perfect then only you can find out the problem. What is perfect means using recommended hardware by SWX.
Did you change any of your setting recently before this began to happen.
Sometimes and setting and a certain sequence could cause a problem.
I had a setting I changed and only when I went to do a midpoint line it would crash instantly.
I had used my "save settings wizard" to periodically save settings - especially before I change ANYTHING and using an older version I found the setting (don't remember now what it was). Unchecked the option box and everything worked fine. (SWX2015).
Use the Save my settings wizard to save what you have now.
Then try different options (after you have checked some of the things that others have recommended). Then go through different options and see if anything changes the problem (You can restore your earlier settings once you have used the Save my settings wizard. I try to do a new save (save files in different folders by date so you have a history of the changes) every so often and then can always go back in time with the settings.
This should especially be done when upgrading or before installing a service pack as these could change some of your settings.