Unconsciously making faces

Sometimes when I'm walking to school or eating dinner or doing whatever, I would think of something funny and suddenly either a) burst into laughter or b) smile to myself like an idiot. Either way, I look crazy and people probably think I need to go to a mental hospital to get help.

Anyone else do this? Where you're just doing something and your mind wanders somewhere else, and suddenly you're thinking back to that time you did something funny and cringeworthy, or you're thinking about something funny someone did or say. And as you're thinking this, you're either unconsciously smiling to yourself or you outright start laughing. Like you'll be thinking something, but it goes beyond thinking, and your thoughts and emotions come up on your face when you don't intend on it showing. I feel like I do this all the time.

Like when someone is talking to me and they say something that's obvious to me (but not to them), I'll make the are-you-serious face in my head, but that look will accidentally surface and suddenly I'm looking at that person with that face on my face. And now they feel bad for even saying anything and they'll think I'm mean or something but I'm actually not trying to be.

The other day, I was eating dinner with my family at home (luckily it was at home and not in public). We were talking about something (I don't remember what) and instantly I thought back to a time I did something super embarrassing, and I started laughing. For a good 2 seconds, I didn't even realize I was laughing out loud. You know how sometimes you think of something and you make comments or faces in your head, so that no one will know what's going on? So I thought I was laughing in my head, but turned out I was actually laughing out loud, and everyone at the table stopped talking and turned to look at me. They had an utterly confused look on their faces, and I was forced to push down my laughter. Then came the hard part. Should I explain to them what I was thinking about and tell them why I was laughing? Or should I just play it off cool and avoid wasting energy explaining something they were not likely to understand? So I tried to explain it and I was laughing as I talked and everyone just stared and made the I-don't-get-it face. Oh boy, that was awkward.

Just yesterday, during my spare block, I was sitting at a table with my spare block buddies, and it was during the break so there were a lot of people in the lounge. I was super tired then, so I closed my eyes and put my head down for a few minutes. When I lifted my head, someone I'm not very fond of was sitting at the table directly in front of me, and was facing my way. In my head, I was like ugh, not again! and was slamming my head against the table (imagining, not actually slamming my head). And I must have really wanted to slam my head against the table, because the next thing I knew, my head was falling towards the table. Luckily my arms were there to soften the blow and I kept my head down and pretended to sleep instead of  raising my head again to slam it down in annoyance.

I hate it when I unconsciously make faces or do things, because to me, I know exactly what's happening, but to others, I don't even want to imagine how crazy I must look to them.

Is there a way to keep from unknowingly doing stuff that's in your head and looking like fool laughing or smiling to themselves? If there is a way to prevent this, let me know.