what should I do if I've been terminated with no reason or warning?

Indiana is an "at will" employment state, which means that your employer can fire you for any reason.  However, they can not fire you for a discriminatory reason, such as your race, color, national origin, gender, or age (over 40).  Employers will often give a non-discriminatory reason for termination, but they don't have to.  If you think that you were fired for a discriminatory reason, you should speak to an attorney that practices in the area of employment discrimination.  The Equal Employment Opportunity Commission (EEOC) enforces federal laws that prohibit discrimination.  The website for their Indianapolis office also contains some excellent information regarding an employee's rights, and can be found here.