That's really random. You must be new to modding Bethesda games.
If you are making it to the main menu and are able to try and load a game or start a new one, then it's not a missing master file for a mod. You will want to check your load order. There is a good tool for that called LOOT https://www.nexusmods.com/fallout4/Videos/5129/?. Run it. It's safe. A lot of people use it for modding Skyrim and Fallout. I use it.
After checking your load order, be sure that you have ALL of the required mods for all of the mods that you have loaded. What you are describing may be a skeleton problem, meaning that you don't have a good skeleton for some actor body for some mod that you downloaded. This can lead to Havok engine errors, which will result in a CTD. If you are using CBBE or something like it, make sure that you followed all of the installation instructions exactly.
Lastly, it's a good idea to use a mod installer and organizer tool. Nexus Mod Manager (NMM), available from nexusmods.com, is a good tool. I use it. Some people prefer Mod Organizer (MO), which is also a good tool. MO is available as a mod download from nexusmods, while NMM is a download from nexusmods directly that their staff has developed, links for it are on the top banner of their site. There are more guides available for MO than NMM. NMM is meant to be an easy to use solution, while MO allows more customization and control of what is loaded and how it gets loaded.
If none of that works, or you just don't fee like trying it, then start removing mods until your game works so that you can figure out which one is breaking it. Trial and error will help you to find out what is breaking your game, but not necessarily why. A missing other mod dependency or a bad load order can easily make your game crash, so changing the load order of a mod that is crashing your game can sometimes make it stop crashing most of the time or even make it stop crashing completely.