When Bilbo escapes from the goblin caves in The Hobbit he doesn't tell anyone about the ring on purpose.
They wanted to know all about his adventures after they lost him, and he sat down and told them everything--except about the finding of the ring ("Not just now" he thought)
What made Bilbo hide finding the ring from the dwarves? He really had no reason to. Was it the power of the ring already taking him?
From the text, it appears as though Bilbo is just glad to finally have their respect and praise (emphasis mine):
"And here's the burglar!" said Bilbo stepping down into the middle of them, and slipping off the ring.
Bless me, how they jumped! Then they shouted with surprise and delight. Gandalf was as astonished as any of them, but probably more pleased than all the others. He called to Balin and told him what he thought of a look-out man who let people walk right into them like that without warning. It is a fact that Bilbo's reputation went up a very great deal with the dwarves after this. If they had still doubted that he was really a first-class burglar, in spite of Gandalf's words, they doubted no longer. Balin was the most puzzled of all; but everyone said it was a very clever bit of work.
Indeed Bilbo was so pleased with their praise that he just chuckled inside and said nothing whatever about the ring; and when they asked him how he did it, he said: "O, just crept along, you know-very carefully and quietly."
The Hobbit Chapter 6: "Out of the Frying-Pan Into the Fire"
