How can my Windows 10 connect to 'Personal Hotspot' of my iPhone automatically
The problem is with the iOS Personal Hotspot feature. By design, the network is discoverable only when the Hotspot screen is open. This means that your PC can't find the network when waking up/rebooting. Unfortunately there seems to be no workaround, I was looking for the same thing for my old car stereo, and I ultimately ended up getting a dedicated personal hotspot for it.

The only workaround is to open the Personal Hotspot screen every time you restart/wake up the PC.