1| When posting a thread of troubleshooting nature, it'd be a good idea to pass on your full system's specs. Outside of the motherboard's make and model we don't know if you're talking about the chipset or the CPU. List the specs as:
CPU: (and CPU cooler)
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
2| You would also benefit from us knowing what your ambient temps are.
3| How long before the temps climb back up to 65? It migt also be a faulty/failing CPU fan or that the installation isn't proper.
4| As a side suggestion, you may want to see if the BIOS is up to date. I'm not familiar with that BIOS layout but that platform should allow for granular voltage regulation within BIOS for undervolting.