numbers and characters instead of letters when using keyboard on inspiron mini 1012

Twice in the last few days apparently for no reason instead of letters appearing when I type, numbers or characters appear. It has nothing to do with the caps lock and I don't have a num lock key. These aren't even the top row keys. They are the letter keys that should only be typing small or capital letters. The problem resolves after I do a reboot, but I'm not sure why it happens in the first place. I was wondering if I'm doing something that is causing this or how I can resolve it. Thanks.