I have a CalDigit mini Thunderbolt 3 dock that provides two DisplayPort ports, a 1 Gbps Ethernet port, and a USB (2? I forget) port. I use it to connect two WQHD monitors, Ethernet, and a wired mouse.
It's a real crapshoot whether the dock will properly or fully connect upon cold startup or reboot. Sometimes everything is dead. Sometimes the monitors get signal but Ethernet and the mouse are down. Sometimes only the mouse is down; very occasionally, only Ethernet is down.
About a year ago, I spent multiple hours on the phone in a looong call with a CalDigit support rep. Essentially, we used my system to troubleshoot. We never solved the problem.
With time and observation, I've learned it's best to cold boot (with power connected, my daily work configuration) with this CalDigit Thunderbolt dock physically disconnected. After Windows has booted and gotten to its desktop, I then wait 90 - 100 seconds or a bit longer before I plug in the dock. Doing this, my success at having everything come up working is 50% or even a bit more.
If dock isn't fully functional, repeated warm rebooting is not too likely to correct this. The best bet is to hard shutdown, maybe wait a bit for whatever capacitors to discharge, and then start the above procedure over.
The CalDigit rep thought it was maybe the Thunderbolt support/configuration in my X1C6 that was/is to blame, but I have since formed the impression that Thunderbolt, for all its vaunted power, is actually kind of a shitshow.
The X1C6 did initially have a problem: It rewrote its Thunderbolt configuration upon every boot, into a kind of physically memory not designed to have a lifespan of that many writes. About a year, as I understand it, was what it took for many users to start having problems. Lenovo did eventually ship a firmware update to stop this behavior, and through circumstances I'll skip I ended up de facto avoiding the problem. My point in mentioning this being, maybe the X1C6's Thunderbolt support is still/also borked in some manner that causes my problem with the CalDigit dock.
But, I'm not too convinced of this. And I suspect CalDigit is using the same chipset that many other brands are using for similar docks.
For all the premium they charge for it, Thunderbolt designers/implementors should... be induced to provide a better result. IMHO.