You can literally search "Martin Garrix shirtless" in Google and get some results...
However, I won't be a complete tool about it. No nudes exist that I'm aware of, but I'll leave these here:
>>>Skip to 1:17 to see he has a pretty cute butt, and 4:45 he is shirtless back stage after one of his shows
>>>He's shirtless in his hotel room for a few minutes in the beginning while talking about "In the Name of Love" (video dates back to prior to it coming out)