If it's really 5 seconds, it's very likely the belt squealing, though this is uncommon with serpentine type belts, in my experience.
I'd agree with the starter sound, other than duration. 5 seconds of a stuck starter is gonna burn up that starter in a real hurry.
https://www.planet-9.com/threads/anyone-encountered-this-screeching-sound-during-ignition-video-inside.99431/
https://youtu.be/gpxd-BL7v2s
Sent from my SM-G970U using Tapatalk