Is my phone sleeping

Samsung S21

I have a few notifications I get only when I turn on my phone.  Not power on, but hit the button on the right side and get it to light up.  Email.  Location notifications.  2-3 others.

In each case, when I contact support/community, they state my phone likely goes to sleep and only shows notifications when I wake it up (turn it on).

I can find no setting for that in my phone settings.  How do I get my T-mobile phone to NOT sleep when the phone is black?