Well, I was having the same problem as you with a lenovo recently upgraded to Windows 10, so I tried to search at task manager if something weird was happening. I figured that each time I got the keyboard lagged the Microsoft Windows Error Reporting process (WerFault.exe) appeared for a second between the processes that were running on my computer.
So I just decided to disable that service and stopped it. Then I needed to restart my laptop and till now (around 15 minutes) I am not having the problem anymore. Here how to disable the service (just use the third option):
http://www.thewindowsclub.com/wermgr-werfault-exe-application-error-windows
At least this apparently is working for me. Good luck!