Not sure if this has been posted already, but if anyone else is noticing high SB temperatures even when sat idle or in BIOS - check the heatsink and fan assembly under the M.2 shield.
I noticed that the one attached to my board seemed loose, in that there was a few millimetres of movement from side to side when touching the heatsink. There are 2 screws on the back of the board which secure the heatink to the board, I tightened those up and now have SB temperatures in the low 50s when idle or in BIOS, whereas before just sitting in BIOS would see the temperature creep up over 70C and keep going up.
I wasn't experiencing any random shutdowns but I hate seeing unnecessarily high temperatures, especially when it's a result of something which seems like simple, poor quality control.