It is good to know that a car radio must be powered on 2 wires. The radio must receive constant voltage on the YELLOW wire, as this is for the radio's memory. The radio must receive switched voltage on the RED acc wire, because this is to switch the radio on and off automatically. So as soon as there is voltage on the RED acc wire, the radio will switch on automatically.

If a radio does not switch on after a while, it usually has to do with the connection and not with the radio. It may be that the fuse of the YELLOW or RED acc wire has blown. Or that the wire has come loose. Therefore always check first whether there is voltage on the YELLOW and RED acc wire, so you know if it is the connection or the radio. It actually does not happen that a radio breaks down after a while and does not switch on again. Although the radio has defects, the radio will turn on in most cases.