2010 IMAC OS High Serra recently started to periodically to crash & restart

See if you have a panic report (file's ending in .panic).  If you have more than 1, please post a couple as the differences can be very useful:

Look for the Kernel Panic reports at:

Finder -> Go -> Go to Folder -> /Library/Logs/DiagnosticReports 

<http://support.apple.com/en-us/HT200553>

The panic report should have ".panic" in the file name.

You can put the panic report in an "Additional Text" box when you Reply

If, AND ONLY IF, you have difficulty posting via "Additional Text"

then try posting to PasteBin.com, and give us a PasteBin URL link.

<http://pastebin.com/>

I'm just guessing, but I cannot see anything else in your panic that looks guilty. I do not even know if your RAM is guilty.

I can tell you that sometimes when there is a major operating system change, memory usage patterns change, and sometimes RAM that worked just fine in an older macOS release, starts to fail.

Keep in mind that many RAM tests hammer on memory electronically adjacent to another memory cell, and then they see if it cause a memory change where no changes were being made. If some memory access pattern now simulates this kind of activity and "Your" RAM is susceptible, then maybe that is why you are seeing.

Again, all guessing.

You could try removing the 3rd party RAM (which would not be very friendly to your Mac's performance), and see if you keep getting panics.

You could try running Rember

www.kelleycomputing.net/rember

Boot into Safe mode, and Quit as many apps and menu bar utilities as you can to give more RAM over to Rember for testing

Set Loops: [X] Maximum

and run overnight.

HOWEVER, if Rember DOES NOT find anything, that does not prove the memory is good. It just means it did not find anything.

There is definitely 3rd party RAM install

Memory Module: BANK 0/DIMM0, 2 GB, DDR3, 1333 MHz, 0x859B, 0x435432473353313333394D2E4338464B4400
Memory Module: BANK 1/DIMM0, 2 GB, DDR3, 1333 MHz, 0x859B, 0x435432473353313333394D2E4338464B4400
Memory Module: BANK 0/DIMM1, 2 GB, DDR3, 1333 MHz, 0x80CE, 0x4D34373142353637334648302D4348392020
Memory Module: BANK 1/DIMM1, 2 GB, DDR3, 1333 MHz, 0x80CE, 0x4D34373142353637334648302D4348392020

Crucial for the 0x435432473353313333394D2E4338464B4400 part

Samsung for the 0x4D34373142353637334648302D4348392020 part

My guess is that you are having a 3rd party RAM failure.

The reports cannot be seen here, just links to where they are on your Mac.

What external drives or cards do you have & how connected?

I'm thinking Bob has likely called it.

Take care Mike. :)