Lemme guess. You got an Android right?
My Sammy's will do that as they load notices, background apps, weather changes, notices, messages, notifications, Samsung Pay, adware, freeware apps that do sundry things in the background, etc. Once that stuff begins bloating up the OS, the GO program slows down as the processor heats up and self-slows itself to keep its cool doing all the work. Only cure is to try and shut all that stuff down permanently by maybe rooting to just the OS Android itself and no apps allowed that take over in the background, and keep the device cool too. Bad part of Android is once you load some app, you also Accept the terms and approve of it to do random things for it to run.