I’m having this exact issue. Ugh! After spending a lot of time disassembling my phone and swapping the port connector cable, it reboots after 3 or 4 minutes. I had ordered a cheap part from eBay because I’ve done that a lot to fix phones in the past but I ordered the iFixit cable this time and will try to write back to let you know if that one works. It costs a lot more but this might be a case of “you get what you pay for”. Update (11/20/2020): FYI, I can confirm that the part from iFixit works and my phone is good as new now!