The problem seems to get worse when its warm inside the car. The radio after the car starts will turn off and quickly back on every few seconds. It is a very annoying issue. Does anyone know the cause or fix?

 

could be a relay, a loose wire or the head unit itself. does it do it when the car is parked or only when in motion? You can try pulling out the radio and put a probe on the voltage to see if you are getting a steady 14V when the engine is running and the car is hot. If the power feed seems solid then I'd suspect a problem inside the unit.