10th gen - up Intel CPU I'm guessing? There's some things you can try, but no guarantee it will fix it.
You can try setting process priority to low and CPU affinity to 1 core for the cxbx-ldr.exe, but sometimes that is not enough to fix bootup gacha and you might need to do extra steps
Courtesy of Frail on WME:
Here's the method that I used involving the usage of Process Lasso:
Step 1: Initial Step,
Press Win + R to open Run window and type powercfg.cpl to open Power Options.,
Choose any power option you don't use, you can either use Balanced (if you don't use it) or Power Saver (if you can't find it, it's under Show Additional Plans), click Change plan settings on the right side of the power plan.,
Click Change advanced power settings, and on the next window find Processor power management.,
Click on Maximum processor state and change the setting to 70% or below.,
Click Apply, and then OK to save changes and close the window.,
Step 2: Process Lasso,
Launch Cxbx and run the game, keep it running.,
Open Process Lasso and find cxbx-ldr.exe process, right click on it to show several options.,
Go to CPU Affinity, select Always, on the next window uncheck everything. Then, only check CPU 0 and CPU 1. Click OK to save changes.,
Next, right click cxbx-ldr.exe again and go to Application Power Profile, select power plan you just modified from Step 1 above.,
Changes should apply automatically the next time you ran the game. Now you can close Cxbx.,
Relaunch Cxbx again and try launching the game to see if you have succesfully entered the game's bootup screen. If bootup screen does not appear, keep relaunching Cxbx until it appears.,
If bootup screen appears, go to your Taskbar Tray Icons, find Process Lasso tray icon, right click on it and change power plan to your default power plan.,
Game should run properly.,
The next time you launch the game it will apply the setting you set on Process Lasso as long as Process Lasso is running in the background (or it's Core Engine). You just need to revert to your default power plan everytime the game has succesfully entered bootup screen.
Pros and Cons of using this method
Pros: Changes apply automatically and easily switch power plans with just a few clicks.,
Cons: Process Lasso is not free, and it doesn't entirely eliminate bootup gacha, only reduces the chances of it happening.,
Who is affected from this Bootup Gacha?
For now only users with Intel CPUs newer than 10th Gen is having this issue. AMD CPU users does not seem to have this bootup gacha issue even on newer CPUs.
If you're having this issue consider doing the method explained by dmr above, or this Process Lasso method.