Interesting.
Spoilers 2,3&4 deflect upwards about five seconds after lift-off. These are the speed brake panels, selectable by the speed brake lever. For roll control Spoilers 2,3,4&5 operate together (have a look at HD US A320 out of Phoenix Sky Harbour, after T/O, on the same channel).
SEC3 controls spoiler 2, SEC1 controls spoilers 3&4..these two are at the same angle, a different angle to spoiler 2.
Deduction.... this is a small speed brake demand which occurs when Normal Law blends in after lift-off.
My GUESS as to why... Do United still disarm Ground Spoiler immediately on L/G retraction selection, or do they wait until Flaps Zero (airbus SOP since several years ago)? If the PM disarms the Ground Spoilers with a vigorous push it is possible to select a small speed brake demand without realising it...
Of course I could be completely wrong about the "why".