I am 37 years old, and just found out that my father has tried to cash out a UTMA that he created for me. He won''t sign the transfer of ownership.

I am not sure what your question is. Assuming the account was created under Georgia law and is being held in Georgia, you became entitled to the funds in the account years ago. If it's not Georgia, the same answer probably still holds true, but I'm only licensed in Georgia so I can't address other states. Unfortunately, if your father will not willingly turn over the funds to you, your only recourse will be to sue him. That won't be a pleasant process. You can try and ask him again for the funds, and tell him that you will not hesitate to sue if he continues to refuse to turn over the account. But if you want to preserve a relationship with him, you may have to let this go. Unfortunately, this is not an uncommon situation. Good luck to you.