405mhz

I have a pretty old system (+8 years) and some days ago my gpu began stopping at 405mhz at gpu and memory. if i just restart pc there is normal (810mhz 500mhz (irl 499mhz idk why)) but if i turn off pc and turn it on the problem is back. i overclocked my card to 880mhz gpu (idk why its 882mhz on...