Frodo was always corruptible, otherwise, there would really be no drama and it would not be such a tremendous achievement that he resisted for so long- key word resist. So what is he tempted with? The books don't tell us outright, but there are clues.
He has abandonment issues - parents dying, leaving him nothing but a place in the Brandybuck familial home, where he is largely ignored and left to his own devices (and later Bilbo abandons him too.) This also leaves him feeling unimportant and unloved. Please note he doesn't get adopted by Bilbo until nine years after his parents' deaths. He is obviously a troubled youth or he would not have been stealing mushrooms or wandering at night.
At his coming of age, he is friends with mostly younger hobbits, so he also has no friends during this time and no real support, as Bilbo is scarcely around and his future friends are little kids at the time. So some deep seated issues begin to emerge here. He is lonely and coping through avoidance and escapism- long walks, theft/indulgence, stories, pretend play.
His avoidant attachment style becomes more pronounced after Bilbo's disappearance. He does enjoy his time as master of Bag End, which tells me he is employing very successful coping strategies, but also that something in him is fed and content. He is happy being in control of his life and he doesn't give anyone the chance to leave him again. Sam is his employee at this time and he doesn't let him in a friend until after the journey begins. Merry, Pippin, and Fatty are his best friends, and still he keeps them at arm's length. He is protective of people he loves, but doesn't think himself capable of doing anything for them, so this namely shows up in his willingness to sacrifice himself for their benefit.
Jumping far forward, in the aftermath of the Ring, his biggest fear and anxiety is being shunned and isolated and in his dream, he tries to remedy that with a lofty self important air, and this is really important.
This is his shadow side; self important, needing validation from others, thinking he knows what's best/being too sure of his own judgement, possessiveness over people he loves and wanting to be theirs in turn (codependency,) over indulgence/greed.
After the Ring is gone, having seen intimately all these things in himself, Frodo does a lot of overcorrecting and ends up (in my opinion) reenacting his trauma again through abandoning his friends and main support network in a misguided self sacrifice, since this seems correct and good to him as it is the opposite of the possessive greed he is so adamantly avoiding. In the end, he doesn't grow from his experience, but is set back tremendously and harmed deeply.