My radio/cd comes on but no sound can be heard on 2005 sts. After a few hours, all is well. What is causing this to happen?

nothing worth reporting
national wildlife refuge
national weather radio

no worries right

i tried but have never heard of it and did a quick search and nothing as well... Post an email to GM, see what those brillant people can come up with... pun intended

Check fuses for radio.

no quick fix there. Dealer would be best option. There have been many issues with the STS, XTS CTS, and ATS radios.
Most problems relate to XM radio, but the issue you mentioned seems to lean toward the "replace it" path.
Best to check with a dealership to see if there is a recall.

When it don't want to start have a friend hit the gas tank while you try to start it, if it starts then it's your fuel pump

You need enter the unlock CODE for extract your CDs; check in your owners manual (any label in the last page .

THEFTLOCK is designed to discourage theft of your vehicle’s radio. The feature works automatically by learning a portion of the Vehicle Identification Number (VIN). If the radio is moved to a different vehicle, it will not operate. If the radio is removed from your vehicle, the original VIN in the radio can be used to trace the radio back to your vehicle.

With THEFTLOCK® activated, the radio will not operate if stolen.

Fot other details can check 2005-Cadillac-STS-Owners-Manual

Hope helps.

the radio has an internal problem it will have to be repaired or replaced

I had the same problem for about five months, sometimes the car started for two months than all of a sudden it make take anywhere from 10 minutes to an hour to get it to turn over. Final analysis (when it finally would not start for two days) a new starter was needed. (2001 Cadillac STS)

I have no clue what's going on with the interior lights coming on. You might want to check the switch in the door that tells the car if the door is open or not. As for the radio cutting out, check the connections from it to the car. When I installed my new radio, I slid it in wrong and it pulled apart one of the wires I had twisted together and that kept my radio from working, so it could be a loose, not broken connection that would cause intermittent operation. It is also possible to have to do with the switch I mentioned. I know some cars the radio will continue to operate even once the keys are removed until the door opens and then the radio stops. I wish I could help more, but these are things to potentially check out.

if its factor bad radio is fried same goes with after market radios the only solution with out spending money to find out is to find a good used factore or get new after market your choice

2005 STS4 In the center console there are audio video jacks. Go to radio shack and grab a cable with audio/video one side headphone the other. Plug into your iPod and put the touchscreen setting on AUX. It's on the screen getting to bluetooth