A respectful form of 'yourself' / 'oneself' used when addressing someone politely; refers to the person themself.
ご自身で手続きをされますか、それともこちらで代行しますか。
Will you complete the procedure yourself, or should we handle it on your behalf?
どうぞご自身の意見を率直にお話しください。
Please feel free to speak your own opinion frankly.
この書類にご自身の署名をお願いします。
Please put your signature on this document.