Under "Settings" my IPhone shows that it's connected to my wifi at home, but There is no wifi in the upper right-hand corner, and I cannot connect to the internet. To fix the issue, I have to turn off my iPhone and restart it.

Thanks, but none of the things that you suggest have anything to do with my issue. Most of the time at home, I am connected and everything works fine. Periodically, for no apparent reason, my iPhone gets confused and drops the connection to the router even though I'm sitting within 10 feet of the router. In settings, everything looks like I'm connected; the network is shown and everything looks good, but the wifi icon doesn't show up on the screen. The only way that I have found to fix it is to reboot the iphone. I suspect it is a software issue with Apple.