I recently bought a Tab S9 FE (SM-X510). It is running One UI version 6.11, Android 14.
I almost always use the tablet for reading, online or books, and use it in Portrait mode. When I shut the tablet down, it automatically changes to Landscape mode. Then when I turn it back on, it starts up in Landscape mode, and I have to tilt the tablet toward vertical to get it to auto-rotate back to Portrait mode.
I have auto-rotate enabled because sometimes I use the tablet in Landscape mode, and auto-rotate works best for me overall. I know (please don't point me to instructions) how to enable and disable auto-rotate. I don't want to disable it.
What I want is for the tablet to stay in whatever mode it is in when I turn it off, and remain in that mode when I turn it back on. I have not found a setting that tells the tablet to respect the *current* mode setting when turning off.
For tablets, landscape mode is considered the default, so if auto-rotation is enabled, the tablets start-up in landscape mode. There is another option available. In Settings>Advanced Features>Labs>Landscape view for portrait apps. This feature turns portrait mode apps ninety degrees and displays them in landscape mode either in a window or in full landscape width requiring vertical scrolling. I hope that you find this feature usable.
It sounds like the tablet is defaulting to Landscape mode when you turn it back on, even though you use it primarily in Portrait mode. Unfortunately, there's no direct setting to lock the tablet in the last orientation when it's powered off.
One potential solution is using a third-party app like "Rotation Control", which allows you to control and lock the orientation more precisely. It can help maintain the last known orientation when you restart the tablet.
Another possibility is a software bug or conflict with a specific setting, as this issue seems to occur even with auto-rotate enabled. If the issue persists, it might be worth reporting it to Samsung support for further troubleshooting.
Thank you to all for your comments. I will be reporting this to Samsung as a request for a new option. My previous Samsung tablet, a TabA 10", did not behave this way. It's a minor nuisance, but a nuisance nonetheless.
Thanks also to MrXGeekX for the 3rd-party app recommendation.
