I won't add much to what already what's been said.
Semi-sly has the barber advice 100%. Although not a huge fan of SMP, it can be horrible, if not done correctly. And I believe you need to shave your head to do it... so if you are going to shave your head, just do it.
I would keep the beard.
I mean do something if it bothers you. Looking at you, some thinning doesn't detract from your looks. I would do the least invasive first, change your haircut.