PC constantly rebooting. CPU overheating?

Question

Processors

Hello!
I have the following problem: I decided to clean the PC, took it apart, removed the dust. During cleaning, I raised the cooler a little, so that it would be more convenient to remove dust from under its blades. Didn't change the thermal paste.
Having collected everything back, I found a problem: when you turn on the PC, the coolers start working, but after a few seconds - reboot ... Reboot occurs 5-6 seconds after turning on. After several reboots, the smell of burning begins to be felt.
What could be the problem? I am inclined to believe that the processor is overheating and its overheating protection is triggered, which is why it reboots. There is no speaker, no special equipment either.
I read on the Internet that the problem is in the thermal paste - it needs to be replaced. Is it true? Since I am new to all this, I decided to ask you if my guesses are correct?

Answer 1

really change the thermal paste.