Your temps are fine for an idle load. The CPU heating up in the BIOS is most likely due to the fact that the metal of the heatsink was ambient temp when you turned it on, and is being heated by the CPU, meaning that youv lost the small benefit of cool metal against the CPU.
Also would hardly call a 3°C change over 10mins a "spike" in temperature
. Your gonna have a heart attack when you stress test the machine and see it spike from 30°C to about 55°C in a few seconds.
Your temps are fine.