Fix Internet Disconnection Issue While in Sleep Mode or Reboot
Method 1: I would suggest you to try the following steps.
1. Right click on start button and select Control Panel
2. Click Network and Internet
3. Click Network and Sharing Center
4. Next to View your active networks click Connect or Disconnect.
5. Right-Click the desired network and select properties.
6. On the connection tab of the new window check "Connect Automatically"
This should allow you to boot your computer and auto connect to the desired network.
Method 2: I would suggest you to make sure that the wireless card is not set to power saver mode.
1. Press Windows key + X.
2. Click Device Manager.
3. Navigate to your network adapter, right click it and choose Properties.
4. Choose Power Management tab.
5. Please uncheck “Allow the computer to turn off this device to save power.”
6. Restart the computer and test this issue again.