Chosen Solution
Today I went to replace my iPhone case. I took everything loose and put it in the new housing. At the first test I realize that the cable of the speaker / charging port / microphone was not connected. So I switched the iPhone of then connected the cable. The telephone is now in a boat loop when the cable is connected. When disconnected, it starts normally. iTunes wont connect ether.
Replacing the lightning assembly seems to be your first and more reasonable step..a bad replacement may cause bootloops at times. Maybe try disconnecting Taptic engine first and see how it goes, had a few giving troubles on iPhones 7.
