This forum is intended for questions about old, pre-G3 hardware, and doesn't get much traffic. Hence it's not the forum where you'll be most likely to get help with your problem. I'd suggest you ask this question in the forum specific to your model of Mac; you'll be more likely to get assistance there.
Keyboards often develop sticky keys. Fortunately, keyboards are also easy to clean.
If you are brave, pop off the key caps using a fingernail file. Unplug the keyboard before doing anything more. Look for spilled pop or some other sticky substance that might be keeping the keys from springing back into place.