I can’t see that in the RSBN video, at 1:45:45 he turns abruptly to the right as he senses a threat toward the right rear of the stage and 1 second later the SS man comes up and gets between Trump and that area. But I think you’re right as he clearly reacted to something he felt and maybe heard. The SS men responded extremely quickly, true pros.
Right after, he thanks someone ahead of him for warning him about the person trying to get up on stage.