Hey, I used to have the same issue all the time with some of the previous models and sometimes even now with my current one - S25 Ultra. First thing I would try and do is looking out for "silent" or these weird "disappearing" notifications. You can monitor these either by going into settings and just type in "Notification History" in the settings search bar and make sure that is enabled. Another option of monitoring random notifications and/or vibrations is through Good Lock which is a Samsung app you can download from the Samsung Store or Google Play Store. It's also a very good & useful app for customising and personalising your entire phone & settings! 👌 There are 2 ways in Good Lock to monitor notifications/random vibrations - 1. "NotiStar" plugin for notifications history or 2. "Nice Catch" plugin - probably more useful in your case as you can track loads of weird and unexplained stuff that happens on your phone! So as soon as the random vibration happens again you can go into the app and should be able to see what's caused it! Give a try a let us know how you got on! Hopefully this will help! 😊 
