shortcut or automation for timer

So basically I have this issue where I can’t fall asleep until I’m really tired, I usually scroll TikTok until I’m tired enough and fall asleep with my phone in my hand but the issue is if I set a timer/alarm for let’s say 6 hours and don’t feel tired enough and fall asleep in like an hour after I set the alarm, I be tired when I wake up, so I was thinking is there a way to set an

automation/shortcut or maybe an app that would automatically set a timer for 6 hours after the phone screen is locked for let’s say 5 minutes?