We still have not received the most important info:
70C in idle or under load?
Idle, this CPU should remain between 30-40C, but that only happens when you have a proper 3rd party cooler. With stock one it is easily 10C more when idle.
If you get shutdowns even when idle, that can mean one of the following:
- Your cooling is not properly installed (no contact or improper contact)
- CPU fan is not working
- Voltage on CPU is too high
- CPU is faulty
Also, you can most certainly change the CPU overheating protection temperature in BIOS. IDK what is the default one, but you can change it. However, that won't fix the underlying problem, it will only allow your CPU to reach higher temps and then most likely shutdown as well. Check your cooling.