Safari No Internet Access Periodically

In that case I suspect something system-wide is going on. I will ask the site moderators to move your question to the iPhone Community since the problem is affecting everything, not just Safari.

In the meantime try resetting that iPhone's Network Settings according to Reset iPhone settings to their defaults - Apple Support. That often fixes problems such as this.

Do not reset anything else, not yet anyway. Be sure to choose Reset Network Settings. Review that document first so that you will know what to expect.

"[...]Safari will state not connected to cellular or WiFi unable to load page. Web pages will not load at all. The only way to resolve this is to shut down and restart the iPhone.[...]"

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Profiles:

The first thing that comes to mind is a profile set up to make this occur. But, being that a restart fixes this, that would single that out, meaning it would not apply.

Rid of "System Data" (Formerly Called "Other"):

System Data is composed of caches. Caches are created for remembrance of application usage and operability. So, clear them, and see if this fixes this. Use my User Tip: How to Clear "System Data" in your iPhone's Storage - Apple Community

Is the problem exclusively limited to Safari? In other words all other Internet-dependent apps work including Weather, Maps, etc? Wi-Fi shows "Connected" with no ⚠️ symbol or anything?