Why Keyboard suddenly starts typing (-) automatically?

Windows 7 on acer laptop using latest version of Avast - when entering text, whether a text box online, word doc, anyplace where i’m entering text, system will suddenly start entering slashes (-) and run on until i hit Del or Backspace. i must then delete all of the - (unless they are still running out of control). once they stop, i can continue typing but then it will arbitrarily start doing it again.

VERY ANNOYING!!!

Sounds like a sticky key to me.