I would suggest that you discover your personal writing quirks. I will try to illustrate this with my own experience.
Since high school, I had developed this habit to put aside a notebook (maybe an extra one left over from the school-work books) or a diary (maybe some complimentary office gift given to my parents) and use it to record my thoughts. It was a journal of sorts. I liked to write, and I wrote down all sorts of things, random thoughts, quotes that especially struck me, reminders, tasks, plans, records of my video gaming achievements, etc.
Then somewhere around college, I fully embraced the prevailing digital paradigm, and most of my writing, be it academic, assignments, fiction, journal, all migrated to the keyboard and screen. But very soon I felt the need for something else, another writing medium which allowed me to do things that I could not do (at least with any degree of fluency) on the keyboard.
This was because while writing in those notebooks/diaries, I had developed a host of quirks that allowed me to express myself more fully. These may include anything from abbreviations, variations in font size (sometimes in the middle of a sentence) to represent the importance of something etc., arrows, floating text, boxes, diagrams (which I thought represented my thoughts to the highest degree of accuracy that would be immediately apparent to me when I later read them), silly little inside jokes e.g. I had created some recurring abbreviations/symbols to remind myself of the significance of something, like if something was drastically important, I put a big 'IMP EXT' (important in the extreme) next to it with a 'TM' on top of it to signify that this was one of my 'trademark' recurring signs, and so on.
It was these quirks which I could not recreate while typing that made me put aside a special notebook which I have had for quite a few years now. I don't write very regularly because most of my writing is nevertheless dominantly on the keyboard, but once in a week or two I do find myself returning to the notebook to just write and express some thoughts which I feel the keyboard won't do justice to.
So maybe you need to find some similar and deeply personal relationship with pencil and paper-writing in order to make yourself do it naturally once again.