Object of class stdClass could not be converted to string

Trying to run that code:

        $user = parent::me();

        $user->nome        = $this->request->getPost('nome');
        $user->celular     = $this->request->getPost('celular');
        $user->birthday    = \DateTime::createFromFormat('d/m/Y', $this->request->getPost('birthday'))->format('Y-m-d H:i:s');
        $user->cep         = $this->request->getPost('cep');
        $user->rua         = $this->request->getPost('rua');
        $user->numero      = $this->request->getPost('numero');
        $user->complemento = $this->request->getPost('complemento');
        $user->bairro      = $this->request->getPost('bairro');
        $user->cidade      = $this->request->getPost('cidade');
        $user->estado      = $this->request->getPost('estado');
        $user->updatedAt   = date('y-m-d H:i:s');

        if ($user->usertype == 2) {
            $user->bank      = $this->request->getPost('bank');
            $user->ag        = $this->request->getPost('ag');
            $user->cc        = $this->request->getPost('cc');
            $user->profissao = $this->request->getPost('profissao');
        }

        try {
            $user->save(); // line 301

Returning: Catchable fatal error: Object of class stdClass could not be converted to string in line 301

Someone can help me?

Ps parent::me() -> User::findFirstByUser_id($this->session->get('user')['user_id']); Ps2 $user seems to be ok, the error occurs only on save