Fir the last 36-48 hours my Note 20 has been vibrating every 30-32 minutes with no notifications showing or being recorded. It does this no matter what, as far as I can tell. If it's in my pocket, if I'm holding it, if it's charging and sitting still... I've not downloaded any new apps in that time and I can't figure out what is going on.
Also, I've turned the notifications volume up and it signals a notification instead of vibrating. I have restarted my phone, a couple of times to no avail.