Slow display in a popup Taskbar toolbar

I created a toolbar which contains most often used software shortcut
icons. It is tucked in over on the right side and pops up when clicking
on the >> .
On first use it is blank for 5 or more seconds. Thereafter it displays
the list immediately.
Is there an explanation for this view delay considering when the pop up
tool bar (holds the Windows update icon and has a 'customization' link
at the bottom )displays immediately.

RoseW