To find it, you'll likely need to:
1. Consult your owner's manual: This is the best place to start. The manual should have a diagram showing the location of the inertia switch.
2. Check near the fuse box: This is a common location for inertia switches in many vehicles. The fuse box is usually under the dashboard on the driver's side.
3. Look under the dash on the driver's side: Carefully inspect the area around the driver's feet, paying close attention to the kick panel. You might need to remove the kick panel to access it.
4. Look for a small, usually red, square or rectangular box with a reset button: The inertia switch is typically small and relatively inconspicuous.
If you can't locate it after checking these areas, a search online for "1999 Dodge Grand Caravan inertia switch location" with images might yield pictures showing its location in a similar model. You could also consult a Dodge mechanic or auto parts store for assistance.