SCREEN FREEZES EVERY 5 TO 10 SECONDS,WHEN RUNNING FURMARK OR SOME TEST, IT CLOSES AUTOMATICALLY. HELP

Hi, if you have a scope please try to measure the vcore or the 12v power plane, it shouldn't have an high peak to peak voltage. If you don't, please try a very good PSU.
I had this issue on a few 2060 on which capacitor turned bad overtime (was only lightly designed) and the 12v regulation was horrendous, since 1660s are also on the cheap side of the line-up, I suspect they have a very light 12v regulation like on some 2060 and might get similar issues.