GR translation: a poising, an uneasiness

[Mike Jing]

Still going back and forth.

P3.10-18   Inside the carriage, which is built on several levels, he
sits in velveteen darkness, with nothing to smoke, feeling metal
nearer and farther rub and connect, steam escaping in puffs, a
vibration in the carriage’s frame, a poising, an uneasiness, all the
others pressed in around, feeble ones, second sheep, all out of luck
and time: drunks, old veterans still in shock from ordnance 20
years obsolete, hustlers in city clothes, derelicts, exhausted women
with more children than it seems could belong to anyone, stacked about
among the rest of the things to be carried out to salvation.

What is the meaning of "a poising" here?