What is the cause of the fear that seizes me during the night vigil (Qiyam al-Layl) and Fajr prayer, which has increased after the car was stolen from in front of the house, and sometimes prevents me from going to the mosque?

The fear you are experiencing is a pathological fear that must be struggled against and overcome, especially if it prevents you from praying or attending congregational prayers, which are an individual obligation upon men. The cure for this fear lies in having a good opinion of Allah, believing in divine decree (Qadar), and achieving complete reliance upon Allah (Tawakkul). For what was destined to befall you would not have missed you, and what missed you was not destined to befall you. Ibn al-Qayyim explained that whoever abandons managing their own affairs and surrenders their matter to Allah will find relief from worries and achieve happiness and comfort.