In a large stockpot, heat oil to medium-high. Add shrimp, red pepper flakes, garlic and ginger. Season liberally with salt and pepper. Cook until pink, turning once, about 3 - 5 minutes. Remove from pot.
Add oil, shallot and bell pepper. Sauté until shallots are slightly translucent. And remaining ingredients (excluding the garnish).
Increase heat and bring to a boil. Boil until noodles have softened (about 6 - 10 minutes, depending on package directions).
Return shrimp to pot and heat until warmed.
Garnish with fresh cilantro and lime wedges.
Notes
If substituting another broth, add 1 tablespoon of grated ginger and 1 tablespoon of lime juice when adding the broth.