Pop up asking to set up browser

Go to Settings and scroll down until you find the browser app or email app. Tap the app, then tap Default Browser App or Default Mail App. Select a web browser or email app to set it as the default. A tick will appear to confirm it's the default.

Change the default web browser or email app on your iPhone ...

Katyt11 wrote:

I get my phone asking me to set up my default browser! It’s driving me crazy.

To improve understanding of the phenomenon, it would be highly beneficial if you could share a screenshot. Visual representations carry greater impact than written descriptions.

Please remember that this is a public forum, so when attaching a screenshot, please avoid including any personal credentials such as IP addresses, card details, email IDs, Apple IDs, IMEI numbers, serial numbers, phone numbers, order IDs, or any identifiable location information if you are sharing a map.

With the limited information that you have provided, It is hard to even guess the problems faced by you. 

You may get faster and better responses to your query by --> Writing an effective Apple Support Commun… - Apple ...

Please re-post with detail so that someone else can help.