I made an error on 2020 fed return & received $952 refund. T Tax caught error & my refund should have been $2428. Do I need to file amended to receive additional refund?

If this was because of the excluded unemployment or PTC on form 8962 then the IRS will recalculate the return sometime this summer and send the extra refund ... do NOT amend the return.  

What was the error?  How did Turbo Tax catch it or tell you?  They didn't catch it until after you filed?

I entered the wrong federal withholding from my unemployment, 1099-G.

If you have already filed then wait for the IRS to process the return since this is an error they usually catch.   If they don't you can amend later.