Car makes a mechanical noise (once) after 20km/h?

Hello,
I drive a Ford Fiesta Mk7.
Every time I start the car and drive off and exceed/reach 20 km/h, it cracks once, as if a mechanical part is somehow extending or something (hard to describe). However, this only happens once (per car start), so once it cracks once, it doesn't crack again for the rest of the journey. Additionally, when I hear the cracking sound, my lights (low beam) briefly "light up," meaning they become brighter than normal for about 0.1-0.5 seconds. I also feel a kind of resistance in my foot/brake pedal when I brake and accelerate to 20 km/h (the first time after starting the car). My question is, what is this and whether I should be worried.