No. Islam is entered by sincerely testifying that none has the right to be worshipped but Allah and that Muhammad is His Messenger; the moment you believe and say it, you are Muslim in the sight of Allah, wherever you are. Witnesses and a mosque are not conditions of validity — they are simply useful so the community knows you as a Muslim and can help you with documents, marriage, or a future janazah. So say the shahada now if you are ready, and let announcing it publicly follow as a practical step.
Evidence — the daleel
Sahih al-Bukhari 25 ṢaḥīḥSahih al-Bukhari 1395 ṢaḥīḥSahih Muslim 19 Ṣaḥīḥ
On deen2u
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.