In the simplest terms possible, I'm going to cover the basics. The first thing to know is that all the electricity in an automotive system begins and ends at the vehicle’s battery. This is the heart of the system. If you don't have a good battery and perhaps the voltage is a bit low, everything else in the vehicles electrical system will be effected.
Don't rule out engine performance issues here. Your vehicle’s computer speaks in the language of voltage. If it doesn't see proper voltage signals or doesn't have enough voltage to run properly, everything will be affected. This is especially true with newer vehicles that rely on a lot of electronics. Electronics, especially computer-controlled electronics, are very sensitive to voltage changes, especially low voltage. If they don't have enough voltage to operate, they tend to act strange, or, in some cases, even fail.
My point: When dealing with any automotive electrical issue, start with the battery. Check its voltage and its state of charge. A good battery should have at least 12.6V for a static charge. It should also be able to pass a load test and stay above 9V when placed under load. Here are two videos about checking an alternator and a starter on a vehicle where you can put this knowledge to use.
Before we're finished with the battery, let’s talk about one more thing: connections. I would wager that about 90% of electrical failures are the result of poor or inadequate connections. In addition to checking the battery, also make sure you check its connections and cables. I've seen my fair share of electrical problems caused by bad connections. If you have a lot of corrosion at your battery terminals or the terminal isn't tight to the battery, this can cause an electrical problem. Clean and tighten the battery connections and recheck for your electrical issue if this is what you find. Here's a video to help you out.