MacBook Air doesn't want to turn on

My early 2015 Macbook Air (Sierra) doesn’t want to turn on after being off overnight. I can get it to start by following Apple’s instructions for resetting the SMC, but I’m guessing this is a sign of something wrong. Any idea what it might be?

Definitely an SMC problem. But if resetting it doesn’t stick, then there may be a motherboard problem. Since your Mac is 7 years old (and presumable obsolete), Apple isn’t going to be able to do anything for any price, but if you know of an independent repair shop that does board-level repairs, give them a call and have them take a look. It might be something simple like a blown capacitor, which could be fixed for a few cents worth of parts and an hour labor.

According to MacTracker (free, in the App Store), the 2015 MacBook Air is still supported. However, if it needs repair, an independent shop may still be your best bet.