The focus on recommendations
First of all; don't worry too much about recommendations. They matter, but they are not the do-all end-all defining thing that makes you an MVP or not. While I can't speak for all of the internal processes that take place in Sitecore when MVPs are evaluated, I feel fairly confident the recommendation system helps "tip the scale" for candidates that end up in a bit of a grey zone. You cannot rely on recommendations alone to make it through.
Focus on your community work
If you feel you've put in the time and you should be considered for nomination; by all means let Sitecore know about it. And keep focusing on your community work. Don't show up after being almost invisible for a year, in November and start Tweeting like a maniac ;-)
How do I nominate myself?
The application process changed for MVP 2019, and you can no longer nominate yourself. You must get at least one recommendation from an existing MVP or Sitecore employee. You will, receive an email with a link to apply once they have recommended you.
You can read more about the application process in this answer.
The Sitecore social sphere is growing ever faster, and while Sitecore does keep track of what goes on in the community - it is unlikely they will know everything you've been up to during the year. Until you tell them :-)