Opening F3 Search Window and Keep on searching Something

I have a few year DELL LATITUDE E6410 Laptop, windows 7. For maybe a week or so now, my laptop suddenly started pressing the f3 keys randomly on its own and keep on searching something. Nothing Stuck any key on the Laptop Keyboard.  

I scanned my laptop with antivirus, antimalware, and antispyware and it still hasn't gone away. 

The below are connected with my laptop

• Connected internet with my mobile phone via wifi 
• attached external keyboard and mouse (I have to work fast so that I attached external KB and Mouse)

Even I unplug external keyboard and mouse still the same issue has been coming.

Note : also tell me Is there any option there to lock laptop keyboard and mouse and working with external keyboard and mouse.

Please look at below video to better understand my issue. In this video Even I close that windows It keep on opening and searching and not only for search window it will search on my webmail also. whenever I open any programs It will search something.[View:/cfs-file/__key/communityserver-discussions-components-files/3518/Search-issue-2.mp4:550:0]