I suppose it depends on what shape you already have in the 4th dimension.

If you or the current 3d space don’t already occupy any length in the 4th dimension, then you’d simply disappear from the world, or from your point of view, the world around you would disappear. Just like a cutout stick figure on a piece of paper.

Now, you can obviously move a flat piece of paper upwards without destroying the drawing, so if your friend is kind enough to include your surroundings in the dimensional shifting, then you’d be fine. Fly around the 4th dimension in your bedroom or whatever.