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Can anyone tell me how to fix this?
No clue as you've provided no details of what specifically occurs that requires the reboot.
Basic troubleshooting from the User's Guide is reset, restart, restore (first from backup then as new). Try each of these steps in order until the issue is resolved or provide some details of the issues so we can offer more relevant troubleshooting.

Reply something about I have iPhone 4 with personal hotspot but I have keep rebooting my phone to connect to my iPad or computer why or Post a New Thread