I can only launch Fallout 4 once after I start my computer. Why?

I've had this happen a few times on several Steam applications. Typically, this happens when the actual process fails to close properly or hangs in the close process (i.e. if you close the application through the task bar rather than through steam or its native launcher from within steam...) and when there's a memory leak where, if you open task manager you can see how much memory is being used to run the process.

You'll likely notice a disproportionate amount of RAM being used on the specific application you're unable to reopen.

You'll need to kill that, any steam associated process altogether, and any Fallout 4 application specific process (helpers, the exe, etc).

Then check for video driver updates, game updates, and steam updates - but it's usually the result of how you're closing out and less a problem between the systems deployed.