Whisk together olive oil, garlic and white pepper in a large, shallow baking dish. Add shrimp and toss to coat completely. Cover and refrigerate for at least 2 hours or overnight. Preheat grill on high heat. Season shrimp with salt and grill for 2 to 3 minutes on each side. Remove from the grill, place on a large platter and immediately drizzle with aged sherry vinegar and sprinkle with fresh thyme.