i need to restart my mac each time i want to connect to change a wifi connection or use hotspot

Let start by re-creating your network configuration to ensure nothing has changed there.

Step 1: On your Mac, open "System Preferences"

Step 2: Click the "Network" icon (in-between the "Software Update" and "Bluetooth" icons)

Step 3: Click the Wi-Fi configuration tab (it may say Connected if you're currently connected to Wi-Fi)

Step 4: Click the "-" (minus) button at the bottom of the list (this will disrupt your internet and local network connection)

Step 5: Click the "+" (plus) button at the bottom of the list

Step 6: Select "Wi-Fi" from the "Interface" drop-down list

Step 7: Click the "Create" button

Step 8: Click the "Apply" button (at the bottom right of the box)

Your Mac should re-connect to your router automatically, if not, re-connect manually.

Tip: If you're sharing a hotspot from an iPhone, plug the phone into the Mac via a lightning cable and turn off Wi-Fi, this will act like a wired connection and has been more reliable for me.

Thanks

Try creating a different network location for each different network/hotspot.

See:

How to use network locations on your Mac - Apple Support

http://macs.about.com/od/networking/qt/networklocation.htm