Ghost surges.

I had a few of those. One guy beside me asked why my truck jumped and I told him it was that wicked acid that doesn't like being in a confined space & it wants out. Can't describe the look on his face.

 

What a strange phenomenon. Never had surge after 2 minutes of being parked. I usually haul the same 15 or so chemicals though. Sometimes if I pull forward from the fueling lane and get out right away, the truck will jiggle and almost make me fall lol. What were you hauling?

 

I got those from time to time at a previous company. A very subtle air leak in the air ride was the cause. Couldn't hear it, but it was enough to cause the trailer air bags to slowly deflate, which causes the trailer to push the truck forward. It actually has enough force to overpower the trucks brakes for a split second and shift the truck forward a little, usually with a 'pop'.

 

Don't know what Ethos was hauling, but I was hauling phosphoric acid.
I thought about it and decided maybe it's caused from wind gusts, but takes awhile for the energy of the wind to transfer to the liquid. Not unlike a tugboat pushing the side of a large ship. You'll see the tugboat pushing hard and the water churning from the tug screws, but the ship isn't moving. The tug will back off, then a few seconds or minute later the ship moves sideways. When the tug initially backs off, you wonder why he stopped pushing before the ship started moving, then you figure out it took awhile for the energy to transfer from the tug to the ship.
Maybe I'm tired and over thinking it.

 

I bet it's happened to me, but I was asleep and didn't realize it.

 

Yup happen to me, at first I thought someone bump me. It has to do something with the air ride on the trailer.