Switches to the run activity screen randomly

Could you describe the issue in more detail?

Are you saying that you are at the watchface and all of a sudden you are at the run activity screen? Could you've clicked the start button two times without noticing? 
How is the watch placement? Do you have the watch about 2 fingers from the hand as instructed? If you wear the watch like a "normal" watch it is easy to press the start button by accident when you twist the wrist upwards.

e7andy said:

Could you've clicked the start button two times without noticing?

It is also possible, that the button is damaged, and triggers by itself.

I've seen the same issue on my 945 as well. Not related to any accidental button pressing. It's not consistent for me, but your description of how random it occurs makes me think it's a software bug.

It has never happened to me and there are no more reports about it in the forum so I don't think it is a software issue. More likely a hardware issue or caused by the user.

I'm reporting it, so does that count? 

As for my case, it had nothing to do with an accidental button press. Plus, it was the run activity screen showing up immediately, not the activity selection screen. I would think that an accidental press would lead to the selection screen.

I agree it could be a hardware issue...these button are pretty low quality.

My two-month old Forerunner 255 also randomly switches to the run activity screen.  It did it just now as I was sitting at my computer.  It is also 5 hours off on the sunrise/sunset times while the clock is spot on.  (I have tried doing an activity with GPS to "reset" the sunrise/sunset issue with no luck.)  

Anyone know how to correct either of these?

What is your location setting for the Sunrise & Sunset widget? Make sure it is set to Current Location. 

I don't know what you mean about setting the location for the sunrise & sunset widget.  I can't find any instructions to do so.  I did set save a location with that widget but it did not correct the problem.

View the widget and then hold the up button to get to the settings. 

Setting the location did not work until I cycled power and not it appears to be working.

Thank you.

Now about the random run activity...