Why Does this Bird Keep Face-Planting my Window?

I woke up this morning to the sound of something hitting my window, I figured it was a one-off and tried to go back to sleep. By the fifth time it happened I was reasonably annoyed and slightly creeped out, the next time it happened I tried to pull the curtain back really quick to catch whoever it was (I thought someone was throwing stuff) but I didn’t see anything so I took the curtain down. Next time I saw a flash of wing as I looked up so I set up a camera. I’m %90 sure this is a robin and from what I know of them I have no idea why it might be doing this. Does anyone have an explanation? Is it sick or something?