Str de345 shuts down after a few and flashes (protection) on face of amp.

This usually means there is a short in the amp section. It needs to be looked at by a pro.

Your device has went into protection mode, an internal malfunction causes it to shut down in order to protect itself.
Somtimes a physical reset will help.
Turn of and unplug device fro a couple of hours

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/jason_77a19afa8d604dee

If it's not heat you may not be able to resolve it yourself. A technician might.

The manual says it thinks there is a short circuit on the amplifier output side. If it still says Protect after disconnncting all the speakers wires there is an internal problem. Take it to a hands-on tech.

If the problem disappears, you had a short. Attach speakers one at a time to isolate the cause.

http://www.retrevo.com/support/Sony-STR-DE345-Receivers-manual/id/387bh943/t/2/

Sony receivers in this series do a series of tests on the integrity of the audio path before allowing voltage to be applied to the output transistors.
First make sure the speaker selector is set to "off". Test it again. If it still does the same thing then:
If you are comfortable removing the cover, take out the four side screws and the screws on the rear top of the cover. Look at the volume control and make sure the ribbon cable is firmly inserted in to the slot at the back of the control. The next part is a little more involved. There are two ribbon cables on the circuit board on the front of the face plate. One is close to the front, the other is not. You can remove the face plate and check thoes cables, but you must remove the screws from the bottom of the face plate and the one screw holding the volume control in place.
If this is all in place, I recommend sending it in to Sony for repair.

shorted outputs. it needs parts replaced in the main amplifier section. typically $ 120.00

the clicking is a power suplie overload some output amp is with problems and shutdown after overheat, when you tap is bad connection inside, normaly is related with sound off after 15min. needs to be checked by tech. to ensure perfect operation.

es posible que un canal se ha dañado por lo que primero daño el fusible con la sobrecarga y posteriormente se daño el canal. es necesario se revisen las polarizaciones de los transistores para determinar el canal dañado,es seguro que el daño se encuentra en uno de los frontales.

Dust the cabinet out with one of those cans of "dust off" compressed gas and make sure you have PLENTY of ventilation around the amp.

The protect circuit is doing it's job....probably the amplifier
output stage is shorted.....have a technician check it..make
sure any / all bad connects are soldered when chassis is out
for service......................T.