So you are trying to OSDnew machine using SCCM. The machine boots from PXE and starts loading WinPE. You see WinPE SCCM background image with a window ‘Windows is starting up‘ after that you briefly see message ‘Preparing network connection‘. The message disappears and you only see the background, and then system reboots.

In the task sequence log file smsts.log you find the error messages:
Failed to download pxe variable file. Code(0x00000001)
PxeGetPxeData failed with 0x80004005

This means that WinPE Boot image does not have required network card(NIC) driver in order to access SCCM servers.

To solve the problem, you have to download NIC drivers and add them to Boot image. I have created a separate post how to do that.