First check the power supply performance. If the power supply has been used for several years, or the power supply performance is poor, or the capacity of the power supply filter capacitor decreases, it will cause such problems, mainly poor thermal stability.

Secondly, if you have recently replaced the CPU fan, check whether the thermal grease between the CPU and the heat sink has dried up. The second step is to check whether there is a capacitor bulge on the motherboard