Hi Vicky, this may be just an error/bug in Windows, however that is generally an indicator that your system is busy in the background . . .
Open Task Manager (Ctrl + Shift + Esc)
If necessary, click on the Processes tab
Leave that window open to monitor your system
When that busy indicator is on your pointer, is your Hard drive, CPU or RAM overly busy (high percentage) at that time?
If so, click on the appropriate column header, so the arrow faces down
What are the top 5 processes at that time?