when u say burnt what do u actually mean. overheating or burnt out?
if its burnt out you wont even be able to get to the bios screen in most situations unless the machine has more than one CPU.
overheating can be prevented or reduced by using termal paste and allowing better airflow in the machine. if neither work upgrade the CPU fan/heatsink or fit water cooling
I think you should try to identify the problem first and then try to find solutions, not the other way around So unless you 100% know that you overheated it, you should first try to figure out the problem. Anyway since you're asking, I'm guessing you shouldn't even be able to boot a pc if a cpu is burnt (pretty much dead in other words). And talking about cpus, it's also important what model are you using, because if I'm not mistaken, lets say a bit older amd models can reach higher temperatures without damaging it than other models, so it's also important to take into consideration the model youre using.
There are also programs that will display your computer’s temperature. Such programs just read the sensors inside your computer and show you the temperature value they report, so there are a wide variety of tools you can use for this, from the simple Speccy system information utility to an advanced tool like SpeedFan