This days Male and female can't be trusted anymore I've trust several people which later on betrayed me I contacted and explained my problems to him immediately which he got my job delivered within 24 hours I'm so glad I followed my instinct.
Similar to my experience. Luckily I didn't manually restart my watch yet but my back button stops working after a while, the notification preview is not working anymore and the water mode can't be exited (button press works but not button hold). Instead, after a couple of tries the watch crashes and reboots.
This makes me assume, the buttons are becoming irresponsive/deactivated, that's why you can't use them to turn them on.
Samsung has acknowledged that the latest update for the Galaxy Watch4 and Galaxy Watch4 Classic can cause some units to stop working entirely. Although the company has not necessarily resolved the software issue, it claims to have halted the update rollout and is taking steps to remedy affected smartwatches.