That's two actions Neb; which would you do first?
There are a number of possible, and viable, reactions; including, but are not limited to:
Scanning the area to determine the reason you've been wrenched out of your seat. Supposedly the Engineers respone.
Moving your shuttle further from the nebula/nothing. (Meaning you assume it was the nebulaes doing) Supposedly the Scientists response.
Taking immediate evasive/aggressive action. (Meaning you assume it's an enemy vessel) Supposedly the Tacticians response.
RUN AWAY. (AKA, The Cowards Response)
And bouncing a gravaton particle beam off the main deflector dish. The "Make S**t up as you go Along" Response.