If you can not imagine, can not make a mental picture, you can not draw. It's called Aphantasia[1].
[1] https://www.facebook.com/notes/blake-ross/aphantasia-how-it-...
[1] https://www.facebook.com/notes/blake-ross/aphantasia-how-it-...
Even if you're not drawing from something you can see, you can have a procedural memory of how to draw the thing, and you can see what you've already put on the page, and experiment if necessary using an eraser.
I don't have complete aphantasia, but my visual imagination is pretty weak, and I can still draw.