It sounds like inspiration and writing time are not taking place together for you. As mentioned in a comment, that's not so much writer's block, as remembering you ideas. There is a question for writer's block already: Help! I've got Writer's Block
Remembering ideas that come when you cannot act on them is a common writer problem. There are a number of answers and they all boil down to "make a note for later".
Many writers (myself included) develop a heavy notepad habit. Lots of notepads - notepads in the bathroom, notepads by the bed, notepads in my bag, my coat and my jacket. That works but it is not ideal when you are as disorganised as I can be.
Technology to the rescue. Grab your phone call up a recording app and then make like you are telling someone the story idea. That allows you to "talk to yourself" in public without appearing crazy. It also means that your phone is ready to remind you when you are ready to write.
At work, there are more options. I have often sent myself emails from my work account. If things are a bit slow and an idea is swimming around my head then I would "write an email". Not ideal if you work for a corporation that audits outbound emails. Chrome, Gmail, and the Alt+Tab combo at the ready is the workaround for that little problem. That said, don't let your story ideas get you sacked. That would be bad.
Napkins can work too. While hanging out at a food place (more than once) a friend and I have sketched out story ideas on a paper napkin. People have been doing that for longer than I have been alive (but I shall not tell you how long that is).
The alternative is to work when the muse is with you. If you time is flexible, then you might consider sitting down and writing when inspiration hits. This is actually a very poor habit as you may get very little done but it sounds like it would be a step up to get you going.
TL;DR: Make notes when inspiration strikes.