I'm not even sure what is/was happening. Essentially, there are random things in the/my world, for example (but not limited to) water, that make my character move without any input. 

An example I was able to replicate in my world was me getting pulled towards Water Source Blocks, as if they were magnetic. This would only happen if I got too close (about 1-3 block radius).

When walking on a non-full block, i.e. Farmland, Path Blocks or Soulsand the 'polarity' seems to be inverted. This means that I would get pushed away from these blocks.

Restarting my Game, my Launcher and my Computer have not fixed the issue. This issue is also not appearing whenever I use different versions of Minecraft, nor when I play other games, so it seems to be directly related to this version.

I have seen a similar Bug Report for Pre-Release 2. However it was stated that that Bug had been fixed, therefore I would deem it useful to be notified that it is still appearing.