When you spawn into a map, you can roll in any direction before the map starts.
Don’t really know how it occurs but. It generally happens about 70% of the time. It could be cause by hold a directional key. But that doesn’t seem to be the case.
You Stay perfectly still with no movement.
You move in any direction whether it be forward or backwards.
This bug has been know to kill people before a level starts
Here are some videos of that happening