I’m just about to start minecraft speed runs and need a timer for ps4

There are no timers that I’m aware of that run natively on a PS4. You’ll need to use something like LiveSplit on your computer or the stopwatch app on your phone to time the run. If you want to get a timer on the video, you’ll need to either capture the console with a capture card and use something like OBS to record the run, or you’ll need to edit a timer into the video after the fact.