Tidy my office/workspace.
Move all none work related stuff onto virtual desktop 2 or 3.
Put on film OST's that lack lyrics (The Equalizer, Oblivion, almost anything from Hans Zimmer).
Make fresh coffee.
I've used that routine for over a decade and it's become a habit, once I've done all that I'm ready to work.
Forcing yourself to do some very small change can often get you going. You can make this easier on yourself by noting some easy pieces to do in the future, then picking one of those the next time you want to work on that project.
All I have to do is start working on a problem. After a short time I'm oblivious to what's around me. I often "listen" to music but that's just make the office noise less obtrusive - after a while I don't hear the music.