iMac 27 (2017) - freezes (no crash report kernel)

on iMac 27, 8GB GPU, 64 GB Memory - 2017.

On the latest OCLP and Sequoia.

Facts:

• Currently crashing system at random moments (no peripherals connected, tried keeping different softwares open/closed to test)
• System freezes. Needs a hard boot. Upon hard boot kernel image shows. then turns on. Crash reports show nothing. no history.
• NVPR Rams rested a few times, looked and tried turning off login items just in case.
• disables spotlight completely to see if there is a change.
• Last couple of months I had short lags on the system not thinking much about it. just assumed this was a regular OCLP issue.
• Occasionally I would see red rectangles on Safari while browsing a site. Red rectangles reminiscent of large "divs" of html but clearly not a deliberate effect. Some sort of visual error. they'd go away randomly and show up randomly. no longer show up.
• Not sure what to do. help.