This is Extremely common with the current pandemic and strange economic fallout as a result. Jobs are not as prevalent, the doom and gloom being reported is very nerve racking, the restrictions forcing us to physically retreat has rocked our world. I have a solid job with great salary and benefits but have so much anxiety that I keep worrying about the what ifs and can even lose sleep over things I'm imagining that have no basis in reality. You got the job! You were chosen as the one! Trust me, the hiring team chose the right candidate. Take comfort in that....nerves starting a new job are a given so keep them in perspective and try all the recommended stress relievers like more exercise, meditation, visualization, deep breathing. Do not watch the news or talk to negative people. Stay away from all neigh sayers who spread stress. I know exactly where your head is at and I'm right there with you.. These are difficult times & our nervous systems are taking a beating. Your new opportunity is raising your bar of things you could lose (in your head). And is robbing you of some joy. You have to use ways to balance it out.