Why is he touching me when talking?

There's this male colleague from another department whom I seldom talk to.

One day, he leaned in close to my face and touched me lightly on the arm while I was telling him something. I didn't know him well (still doesn't) and having seen how he is very close to another female colleague, just thought this might be how he is. Though the touch did feel intentional.

Today, he asked me something and touched me lightly on the arm again. Then his touch extended to the small of my back.

It were light touches, but unnecessary when we were talking about the most innocent and unrelated stuff.

Why could he be acting this way?

Updates
1 y
PS: I am fat and ugly, and in no way attractive. While he, thought not conventionally good looking, does have his own charisma and is in a popular position
Why is he touching me when talking?
Post Opinion