There is a lot we still do not know about the ball python species. Animal behavior is so hard to predict especially that of a reptile. There is no way really to know what your ball python is feeling. As adults ball pythons are more adventurous looking for mates and prey. As juveniles and hatch lings ball pythons are more likely to be timid and exhibit the actual ball python behavior to which ball pythons get their names by using its coils and covering its head in the coils. So for all we know it could be thinking your arm is a tree limb and it is surveying the land.