What should I pay attention to if the computer suddenly turns off?

Question

Iron

The computer suddenly shuts down, then starts to restart. When the computer is turned off, a sharp click is heard in the system unit. It used to happen rarely, but now it happens much more often.
1. What to pay attention to in the system unit?
2. What programs to diagnose?
UPD:
There is no video card with the system unit. The computer has a minimum number of components.
I did not find swollen conders.
Removed the dust. I will continue to monitor the status.

Answer 1

Most likely the problem is in the power supply.