Siri can easily set timers for you if you just ask. Not only that, if you need to change a timer, restart it, stop it, or just view it, Siri can help you with those kinds of things too. Just like setting a timer with Siri's help, all you've got to do is ask!
How to edit an already running timer with Siri
- Press and hold the Home button or say "Hey, Siri" on your iPhone or iPad to activate Siri.
Say something like "Stop timer.", "Restart timer.", "Show timer.", or even "Change timer."
- Depending on what you asked, you may have to tell Siri what changes you'd like to make.
If no changes are required, Siri will simply confirm that your request was made.
Note that restarting a timer isn't starting it over, but instead can only be used if you've stopped a current timer. Telling Siri to restart a timer simply picks up exactly where you left off when you paused or stopped it.