I’m having this same exact problem every time I start the Running activity, except for the first time (I’ve had this tracker for two weeks). The other activities I do - walking and yoga - seem fine. If I get a big goal, like “3 Day Streak” or something like that, it’ll finally get me out of that screen. Haven’t tried plugging it in because I’ve been lucky enough to get these notifications before my run is over.
I also had a blank screen. But I discovered that there was some tiny particles on the back of my Vivosmart 4 that were stopping it from charging. Once I cleaned the charging port it charged up again and was good to go.