Engine problem

Alright, so here's the deal...my engine runs fine most of the time, only got 76k miles on it. When I'm on the gas too, I never have problems. But every now and then when I let off the gas, or I'm just idling, everything starts wobling side to side...from the sounds and watching the motor when this happens it seems like one side of the engine just isn't firing at all. Anyone else dealt with this? Any possiblity it could be my battery being drained from my amp and not having power to idle, or a fuel problem, or what...I've got no clue really. Thanks in advance...