Processor Randomly Clocks from 800-3600 Mhz

Hello, me name is Finn
Im having a major computer issue right now. I am using a AMD Phenom II Hexcore.
I have been using my setup with this processor for 3 months without any issues at all. Then one day, my computer decides to shut down randomly... I tried restarting it, but it wouldnt get past BIOS before it shut down. The same thing would happen each time, but at random time increments. It turned out my processor which should be running at 60-65 C is running at 75 C stable. I got lucky one time and logged in, and checked the clock speed- the processor was switching randomly between 800 mhz and 3600 mhz every couple seconds, while not working on any tasks(no applications running).

I was wondering, if i get lucky and log into my computer again, should I reinstall BIOS? would that cause any programs to be wiped or any damage to my computer?

CPU: AMD Phenom 2 x6 1090T

Hey mate, thanks for the reply.

Actually the processor was built to run at 65 degrees- its overheating at 75. right now i cant get the computer to turn on for more than 10 seconds.
When it was on, it was literally overclocking itself. I have a 3.2 gghz processor, yet my BIOS was making it 3.6 mhz randomly.

That would be the Turbo mode kicking in,

Both the AMD Phenom™ II X6 1055T and 1090T come equipped with AMD's new Turbo CORE technology. AMD Turbo CORE technology is a performance boosting technology that automatically switches from six cores to three turbocharged core for applications that just need raw speed over multiple cores. While in Turbo CORE mode, the AMD Phenom™ II X6 1090T shifts frequency speed from 3.2GHz on six cores, to 3.6GHz on three cores, making it the fastest processor AMD has ever created.

AMD Phenom

It turned out my processor which should be running at 60-65 C

Only at load, and even that is close too or at what it is rated for,

AMD Processors for Desktops: AMD Phenom

If it is running that hot at idle then the heatsink needs to be either re-seated with a fresh layer of thermal paste applies, it needs a severe cleaning, or your case has really bad airflow.

Ive been using my AMD with my stock heatsink for 3 months without any issues, yesterday switched to a new stock re applied thermal, still no fix, today i bought a new heatsink that they said should cool it, hope that works

The clock speeds changing is normal, it will only use a high clock speed when required. Though I think it may be shutting down because your CPU is getting hot. I don't know if that applies for AMD as well as Intel.
Have you been doing any overclocking lately? It may be that a component is not being supplied with effecient power. Try the new heatsink and see if it helps.