same problem tonight. Just turned it off after full factory reset. hoping for the best.
I know that this report is old now but my 735XT just started the same behavior. Interestingly it too had just got wet (heavy rain). Tried switching off and then attempted to dry out overnight in rice (works for phones sometimes). This morning watch was completely dead (battery dead I imagine) connected it to charge and it immediately started vibrating again.
Any definitive solutions found to this problem. I suspect it’s a water ingress problem, but don’t have much evidence. Getting pretty fed up with Garmin gear to be honest - love the watch but it’s not reliable. Have had loads of problems with the HRM function
Maybe time to look elsewhere
Update - much messing around and somehow the system went into a self test mode. After this the watch was restarted - showing wrong time and date but no motor vibration. All data lost on the watch but resynched with Garmin Express
Fingers crossed but all seems good for the moment
Same my watch is only a few months old but I was swimming in my pool and it just started buzzing and it won’t stop I’m hoping I can send it back and get a new one
If you connect with the ConnectIQ app it should ask you to install the software if not then there is no new update
Another update - watch stayed quiet for an hour then started beeping randomly and powering off by itself. The beeping stopped once I set key tones off; indicating to me that the problem was shorting out of the buttons. Random behavior/shutdowns continued.
contacted Garmin and hoping for some help.