Keyboard Frozen

Dear Forum Support,

I request your help for a following problem, I have a Dell Inspiron 7437 starting about three weeks ago my laptop started to have the issue of frozen keyboard this issue is not always present but it happens very often. 

The problem is present ussualy at the moment I start my computer, after starting the keyboards are frozen, I can't type anything and I have to re-start and sometimes this works, but sometimes I have to re-start my computer up to three times to make the keyboard respond. As an alternate procedure I use the keyboard on the screen but I really want my normal keyboard working in the ussual way.

I wonder if this is a problem with the settings or something with that I probably change inadvertently.

Please can you help me to recover the normal function of my keyboard.

Thanks for your help