Stumbled upon this weirdest behavior, from time to time, my arduino (UNO) runs gode really slow.

Searching this issue didnt clarify anything, most people have problems with IDE itself. My issue is related to actual board.

Heres a sample of my flow:

 - I compile & upload my sketch, all good
 - first initiation of program on the board seems to be "fast"
 - when i start to "animate" the neopixels it goes 3-4 times slower than it should
 - ill touch the board, and animation goes fast again.

[Here's a clip of that, at the end you'll see the "slowness"][1]

The Touching part, is almost like if i "add" static electricity from my finger to the board, it wakes up and behaves normally.
For you who are curious about (non related) what animation im doing on neopixels, im turning on 15 pixels from 0 to 54. Like a "slide effect".
(Im not using delay, only a delay(30) in the loop, rest of the delays are based on millis())

Is there any general info / explanation that would explain this behavior, like in electronics, arduino boards specifically ?

EDIT: should also add, when printing logs into serial monitor, that slowness also affects the  outputs... they appear as "slow" as the pixels flow. When all works normally, i see pixels change and logs 50times per second (roughly), but in this slow motion, i see pixels change and logs around 20times per second.  Taking out the Serial entirely from the code doesnt seem to have effect.