My car is getting fairly old but still runs.

My car is getting fairly old but still runs pretty good. I had the starter replaced but then I was having problems with it continuously dying on me while I was driving. It seemed to only do it when it was hot out and I came to a stop. I had the battery and alternator replaced. Because neither seemed to fixed the problem. The car sat for a few months before I was able to drive it again and then I changed the spark plugs, oil filter/oil, and air filter. It seemed to run fine until I drove it at night. The lights started to flicker on and off and the interior lights were doing the same or at least getting very dim. The lights on my car dim whenever I use the power windows or cruise control. I get very scared about driving at night considering my lights turn on and off by themselves whenever I run the radio, heater, dashboard lights, or cruise control. I was told it was probably the alternator but I just replaced it and it cant have more then 300 miles on it at this point. It seems to be getting better sometimes but other days I have to drive with no interior lights in the cold with no radio. I hate to keep driving it like this but no one can tell me what could be wrong. Any thoughts? I have gotten many suggestions everywhere from a little sensor to an ignition module to a fuel pump. The service engine light is not on. The only light that comes on is the low coolant and that I know is just a faulty sensor. I would really appreciate any help!