Latitude E5270 Boot loop when using external monitor

Hello, I have a Dell Latitude E5270. I have no real issues when using the laptop on its own but recently, I've been using it more as a desktop PC. It is connected to a BenQ external monitor using the HDMI port. I also have a mouse and keyboard attached to the USB ports.

My problem is that whenever I would boot the laptop with the monitor turned on and plugged in, the laptop will just keep looping and won't boot properly. It would show the Dell logo on the laptop and it would disappear and then reappear. It will keep going like that forever. Note that there are no display on the external monitor during this time. In order to get around this, I would need to make sure that the external monitor is turned off when I turn on the laptop and then wait for Windows to load and only then turn on the external monitor. I will also need to press Win+P and select second screen from the list.

I'm sure the monitor isn't the problem because it works perfectly with my old Vostro laptop. I've also tried using the FN+F8 keys to force my output to the monitor but it doesn't work as well. I have no problems with the monitor when Windows is loaded, only when it's booting up. This problem is really annoying and I would appreciate some suggestions.