The "One Ring" seemed capable of changing its size, which is why Frodo wore it on a chain around his neck - to keep from accidentally losing it in the same way it was lost to Gollum.
The Ring seems to have a desire to get back to its master and Frodo is told not to wear the ring,
because it would allow Sauron to find him. Reading here - putting on the ring doesn't make him easier to find, and there are at least 6 times where he puts the ring on, but it remains that there is a danger in wearing the ring, which is in the ring's benefit.
Sam, with the ring within Mordor says:
He’d spot me and cow me, before I could so much as shout out. He’d spot me, pretty quick, if I put the Ring on now, in Mordor.
Why doesn't the ring attempt to constrict itself onto Frodo (or anybody), so that they are more easily corrupted and its master can more easily find it?
For an incredible amount of information on the nature of the ring, see here