This is a weird one I think. My PC is setup to run with two monitors - a BenQ PD2700U and Samsung Syncmaster 2693HM. Until recently both started up at the same time. For the last couple of weeks the Samsung one doesn't start up till about 2 hours after the BenQ.
I have deleted and re-installed drivers, updated drivers, re-set dual monitor, and everything else I can think off. I think, but haven't caught it at it, that the Samsung kicks in when the screen saver starts.

Not much to go on I realise, but maybe someone has experienced similar.

Tech details below.

Windows 10 Home 64-bitComputer type: DesktopInstallation Date: 10/03/2021 22:27:20

Specification Intel Core i7-8700 CPU @ 3.20GHz

RAM - 16GB

MOBO - Manufacturer Gigabyte Technology Co. Ltd.Model Z370N WIFI-CF (U3E1)Version x.x

Monitor 1 Name BenQ PD2700U on NVIDIA GeForce GTX 1660 Current Resolution 1920x1080 pixels Work Resolution 1920x1040 pixels State Enabled Multiple displays Extended, Primary, Enabled Monitor Width 3840 Monitor Height 2160 Monitor BPP 32 bits per pixel Monitor Frequency 60 Hz Device \\.\DISPLAY1\Monitor0

Monitor 2 Name SyncMaster on NVIDIA GeForce GTX 1660 Current Resolution 1920x1200 pixels Work Resolution 1920x1160 pixels State Enabled Multiple displays Extended, Secondary, Enabled Monitor Width 1920 Monitor Height 1200 Monitor BPP 32 bits per pixel Monitor Frequency 59 Hz Device \\.\DISPLAY2\Monitor0

NVIDIA GeForce GTX 1660 Manufacturer NVIDIA Model GeForce GTX 1660 Device ID 10DE-2184 Revision A2 Subvendor ASUStek Computer Inc (1043) Current Performance Level Level 0 Bus Interface PCI Express x16 Temperature 41 °C Driver version 27.21.14.6231 BIOS Version 90.16.25.00.7a Physical Memory 2047 MB Virtual Memory 2048 MB Count of performance levels : 1 Level 1 - "Perf Level 0"