what if my screen keeps freezing - only turning power off then on releases it but then screen freezes again soon after power is back on

If the support article you arrived here on didn't help with this issue, then I suggest that you try booting up your Mac in Safe Mode. If it can successfully boot up, and stay running, then we can try to troubleshoot what is causing it to power off.

Ref: How to use safe mode on your Mac - Apple Support

If booting up in Safe Mode, doesn't help either, than the next step would be to contact Apple Support directly. To do so, simply select the "Get Support" link in the upper right-hand side of this forum's web page.