How can I be showing a federal and state refund with no withholding or estimated payments made?

I was unemployed and lived off of my savings and < $5,000 in investment income. I'm reporting my investment income, but it is less than the standard deduction. Turbotax is showing me getting a large federal and state refund (largely b/c of medical expenses and property tax credits), but I don't know how this is possible, since I made no payments that need to be refunded. Should I even file taxes? Help!