Software issue - keyboard often not registering key presses

Hi everyone, hoping you can help me solve a mystery!

My Dell laptop often doesn't register key presses on screen when I'm typing, making me have to carefully re-read everything I type before sending emails, etc. This happens regularly, every few minutes at least. But the strange thing is that when it happens, Microsoft spell-checkers don't register a spelling error. Say I type the word registr instead of register - if I do that deliberately, I get the red underline showing a spelling error, but if it happens because the computer didn't register the key press, then the red line doesn't appear even if the word is spelled incorrectly. This makes me think it's probably a software issue rather than a hardware issue.

Is anyone else having similar issues? Or can anyone suggest a fix for the intermittent key press registration? 

Thanks in advance!