Your computer was restarted because of a problem.

Dealing with Kernel Panics

Disconnect any third-party peripherals including any USB hubs. How to use safe mode on your Mac, Use safe mode to isolate issues with your Mac - Apple Support then boot the computer into Safe Mode: Use safe mode to isolate issues with your Mac - Apple Support and Playing Safe- what does Safe mode do? See Diagnosing problems- crash, freeze, panic, or spinning beach ball?, Don’t Panic! Understanding & Troubleshooting Kernel Panics in macOS, How to fix kernel panics after installing OS X updates | MacIssues, and If your Mac restarted because of a problem - Apple Support.

Kernel panics are indicative of possible hardware failure, so you should Check your Mac with hardware diagnostics or AHT. Kernel panic logs are found in: /Library/Logs/DiagnosticReports/ folder.

If you have no success figuring what is happening then you may need to examine the software you have running when the panics occur. Be sure it’s all current. If you must to resolve the problem erase the disk and reinstall macOS. Follow this outline to reset the computer to the factory-new state: Factory reset of your Mac - Apple Support.

Boot Into Safe Mode

1. If your Mac isn’t already shut down, then shut it down and wait at least 30 seconds before rebooting.
2. Immediately, at or before the chime, press and hold down the SHIFT key. 
3. Release the key after the Apple logo and progress bar appear.
4. Safe mode startup is much slower than normal startup, so be patient.
5. When the Login Screen appears enter your admin password. If you use automatic login, then this means you are in safe mode.

mdworker is Spotlight.

Safe Boot from the HD, (holding Shift key down at startup), does the problem occur in Safe Mode?

Safe mode attempts to repair Disks & clears lots of caches, so if Safe Mode works try again in regular boot.

How to rebuild the Spotlight index on your Mac

If searching your Mac doesn’t return expected results, rebuilding the Spotlight index might help.

1. Choose Apple menu () > System Preferences, then click Spotlight.
2. Click the Privacy tab.
3. Drag the folder or disk that you want to index again to the list of locations that Spotlight is prevented from searching. Or click the Add (+) button and select the folder or disk to add.
4. To add an item to the Privacy tab, you must have ownership permissions for that item. To learn about permissions, choose Help from the Finder menu bar, then search for “permissions.”
5. From the same list of locations, select the folder or disk that you just added. Then click the Remove (–) button to remove it from the list.
6. Quit System Preferences. Spotlight will reindex the contents of the folder or disk.

Manually Rebuilding Spotlight via Terminal

If the aforementioned Spotlight control panel approach doesn’t spur a reindexation of the drive, you may need to initiate it manually through the command line. Open Terminal and use the following command string to do so:

sudo mdutil -E /

This basically asks for temporary super user status, which is why Terminal may ask you for your password (it may not if you’ve used a sudo command recently or are already logged in as a super user or root. The command asks the unix tool mdutil to reindex the spotlight database for everything on the computer, including external drives, mounted disk images, etc. To re-index only for a specific drive, use the /Volumes path. For example, for an external drive named “MiniMe,” the command would look like this:

sudo mdutil -i on /

Rebuilding a drive index can take a long time, so be prepared to wait whether you do it through the System Preference panel or the command line.

A Troubleshooting Procedure that may Fix Problems with macOS El Capitan or Later

You should try each, one at a time, then test to see if the problem is fixed before going on to the next.

    If possible, backup your files before proceeding.

1. Shutdown the computer and disconnect all third-party peripherals.
2. Wait 30 seconds before you restart the computer.
3. Resetting your Mac's PRAM and NVRAM
4. Reset the System Management Controller (SMC)
5. Reset your Startup Disk and Sound preferences, if needed, after resetting the PRAM.
6. Test in safe mode to see if the problem persists, then restart normally.  Use safe mode to isolate issues with your Mac and Playing Safe - what does Safe mode do?
7. Repair the disk by booting from the Recovery HD. Immediately after the chime hold down the Command and R keys until the Utility Menu appears. Choose Disk Utility and click on the Continue button. Select the indented (usually, Macintosh HD) volume entry from the side list.  Click on the First Aid button in the toolbar. Wait for the Done button to appear. Quit Disk Utility and return to the Utility Menu. Restart the computer from the Apple Menu.
8. Reinstall a Combo Updater: macOS Catalina 10.15.5 Combo Update, macOS Mojave 10.14.6 Combo Update, macOS High Sierra 10.13.6 Combo Update, macOOS 10.12.6 Combo Update, OS X El Capitan 10.11.6 Combo Update.
9. Create a New User Account Open Users & Groups preferences. Click on the lock icon and enter your Admin password when prompted. On the left under Current User click on the Add [+] button under Login Options. Setup a new Admin user account. Upon completion log out of your current account then log into the new account. If your problems cease, then consider switching to the new account and transferring your files to it - Transferring files from one User Account to another.
10. Reinstall OS X by booting from the Recovery HD using the Command and R keys. When the Utility Menu appears select Install OS X then click on the Continue button.
11. Erase and Install OS X Restart the computer. Immediately after the chime hold down the Command and R keys until the Apple logo appears. When the Utility Menu appears:

     1. Select Disk Utility from the Utility Menu and click on the Continue button.

     2. When Disk Utility loads select the drive (out-dented entry) from the Device list.

     3. Click on the Erase button in Disk Utility's toolbar. A panel will drop down.

     4. Set the Format type to APFS (for SSDs only) or Mac OS Extended (Journaled.)

     5. Click on the Apply button, then wait for the Done button to activate and click on it.

     6. Quit Disk Utility and return to the Utility Menu.

     7. Select Install OS X and click on the Continue button.

Hmmm... AppleMatch & AppleMobileFileIntegrity involved in both crashes... any iPhone, iPad, iPod, Airdrop, or Airplay going on?

The most important for this Mac is the LINE chat history which it must not be lost.

Make certain you have both a Time Machine Back up & a Clone.

Carbon Copy Cloner...

http://www.bombich.com/software/ccc.html

Maybe RAM?

https://discussions.apple.com/thread/250376972

Can't download any of those.

In theory upgrading should not destroy previous data, but for safety have 2 backups first.

Any luck yet?

Any updates?