Originally Posted by
Android Central Question Sometimes the screen freezes up too.
Do you see any consistent patterns in when it shuts down or freezes up?
This could include things like - does it always die at approximately the same battery percentage, and if so does it come back up (as B. Diddy mentioned) at a much lower or higher percentage than it shut down at? Does it tend to die when you are running certain applications, and if so are these applications particularly hard on the battery (do they tend to use the camera a lot, or send/receive a lot of data, or games with heavy graphics)?
One of the most common reasons for a phone shutting down suddenly is a failing battery. They are wear parts and do die over the course of a few years more or less - generally depending on how heavily it is used and overall usage patterns.
First think I'd try is a replacement battery if you don't want to spend a lot of time on diagnosis. There are a lot of fake OEM batteries out there so it's kinda hard to be sure you are getting a great one, but Anker sells a known good one, and there are plenty of alternatives from reliable vendors.