66Nick Said:
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Q1. "2018 MacBook Pro pauses every 3 seconds"
A1. Apparently, the macOS is stalled. To, try logging in while in Safe Mode. In Safe Mode, Login Items do not run at login, certain preferences are set aside, and damaged system files are then reset. So, once logged in to Safe Mode, wait 30 seconds, and then restart your Mac, seeing if you can log in go here: How to Use Safe Mode on your Mac - Apple Support
Q2. "This problem started after the computer was plugged in partway one evening which I think 'burnt' out one of the 4 USB C ports (the one on the right-hand side, nearest the screen, near the `delete` key). This port no longer seems to work to charge the computer/connect a display/etc."
A2. Reset the SMC and your NVRAM:
(Applies to Intel-Based Macs Only): Sometimes when changes are made to the system(i.e. Ports), system configurations (i.e. for Power) become manipulated, technically. So, reset the SMC and NVRAM. Try performing each thrice. It may take sometime, being certain you have the time to perform these resets.
Boot in Safe Mode:
Apparently, the macOS is stalled. To, try logging in while in Safe Mode. In Safe Mode, Login Items do not run at login, certain preferences are set aside, and damaged system files are then reset. So, once logged in to Safe Mode, wait 30 seconds, and then restart your Mac, seeing if you can log in go here: How to Use Safe Mode on your Mac - Apple Support
