buy a digital volt meter and start checking fuses for the radio at fuse panel . if blow replace it . if not blown remove radio from dash check to see if radio is still grounded . if still grounded take the volt meter turn on to dc volts and take black test lead touch to your radios ground the touch the red test lead to the red with to see if you get 12 volt with car on if not need to find out why .. take to professsinal ..
you can also check the yellow wire on radio it should have 12 volts allways doesnt matter if car in off or running this saves memory for clock and station presets.
if every thing is test out right then you need to buy new radio ..
if you dont feel good about doing this yourself find a mecp car audio installer and have them troubleshoot your problem maybe expensive but a good tech could find out problem with in the first 30 to 45 minutes it get 35.00 per hour to troubleshoot car audio system ...