I'm assuming windows 10 is on the system.....

Please type Troubleshoot onto the [Cortana] search box, and then select / run Keyboard troubleshooter.

Please run a Full(Complete) diagnostic test to check all hardware on the system.This will run a stress test on all  hardware devices which goes even deeper to find any possible hardware issues that could be causing the keyboard problem. Please follow steps to run Complete test in the link below.

https://youtu.be/LPxDpsH1eZU

Thank you for the suggestion.  Yes I'm running Windows 10.  I ran the troubleshooter but it did not find any issues.  Perhaps it will only detect an issue at a time when the keyboard is acting up.  The problem is that I could never navigate to the troubleshooter when the keyboard is acting up.  

Any chance you have spilled or dropped anything into the keyboard?

Does it misbehave on battery and plugged in?

Does putting it into a 2in1 configuration and back help?

If you have opened the system a connection problem may have developed?

Closing the lid on that model puts it into a low power mode.  The same status it goes to if you just let the Desktop go dark.  If you let the Desktop go dark and wait a minute and then hit the space bar, does it come back immediately and does the keyboard work better after that action?

If not, there is still a possibility some switch or wiring in the lid might be involved.

That system has a slight delay when doing several different things.  If you do something to cause a system sound, it may be delayed by 2 to 3 seconds.  Trying to swipe or scroll or type can hesitate by about the same amount of time.  What you described does not sound as though it could be related to this situation, but keep it in mind when evaluating your problem.

Of course, there is always a chance the keyboard is defective.  Mine has not shown such a situation although I don't use the keyboard that much.  I suppose the onscreen keyboard works normally?  Also, make sure you are not touching the touchpad and causing erratic inputs.