i have a 1993 bmw 325i and whenever i listen to music, after a while it gets quiet and doesnt make noise, even tho its still playing music, is this a short?

also my tachometer doesnt work always and my emergency flashers go off sometimes when my key is in the ignition but the car is not moving,

also when i use my car alarm button, it shuts off the emergency flashers

so what could possibly be the problem?