What type of slide system do you have?
Does this happen on this slide with either deploying, retracting or both?
Does it have an electric lock?
Here's where I would start:
If you have a rack & pinion system it may be that the 4 or 5 seconds your waiting is because you could have a stripped or rounded off pinion gear. During that 4 or 5 seconds is the time it takes for it to rotate around and grab good teeth on the pinion gear and get the slide going.
The next time it is deployed, I'd crawl under the chassis and carefully inspect that entire system, inspecting the gears, possibly loose wires, and of the mechanicals being loose or anything else visibly that could be causing this.