I have exactly the same problem like this:
https://www.dell.com/community/Latitude/Spacebar-not-working/td-p/6107465

Spacebar, the keys 'n', 'b', the key with "?,/." marks, right Alt and Ctrl, and the bottom row of arrow keys are not working. It all started about 6 months ago when I noticed that some arrow keys are not responding immediately so I had to tap twice or more. A few weeks ago the aforementioned keys stopped working; following all the tips related to software didn't help, so I realized that these keys seem to be broken; then I reseated the keyboard and — not right away — but a few hours later I incidentally noticed that all keys started responding.

Though they still stop working from time to time, it usually lasts for less than 2 seconds. But today they stopped responding again and have not worked for a few hours. So I decided that it's most likely a software problem, and opened this form to ask this question; I have been offered to load the previous content (I began composing it the first time I encountered the problem), I've loaded it and started to type — and all keys have started responding straight away!

What should I do the next time this problem occurs? Why keys stop and start working when they want? Is it the Keys Revolution? I'm afraid. Help.

Dell Inspiron N5110
Windows 7 Home Basic