Just recently my 9 week old son started getting really startled and freaked out when we lay him down on his changing table. He will be in a fine mood, then we lay him down and his arms get all stiff and he starts crying in a very scared, helpless way which only escalates unless we pick him up. What could this be?

It is his nervous system maturing. He is feeling insecure on the changing table.

Have you tried changing him on your bed? All 4 of my kiddos did not feel secure on a changing table and I always used my bed or a blanket on the floor.

I was told that when their nervous system is maturing they will often feel like they are falling. One trick you might try is to lightly press his arms/hands against his chest while he is on the table, and slightly rock him. I agree with J9, maybe try changing him somewhere else.

As both ladies said, your baby is just starting to develop a sense of the nervous system... suddenly all these things that used to be fine scare them.

I switched to changing my daughter on the bed until she was a bit older and got adjusted to this new feeling. I was then able to start changing her on the changing table again, but by then she was rolling all over, so for me it was easier to just stick to the bed or floor :)

My daughter is 11 weeks now and she did the same thing on the changing table when I would lay her down on it. But now that changing table is our talking place more than anything I have a stand lamp that has a bunch of colors on it she stares at it and talks to it all the time now. She throws her hands and startles her self sometimes when she first falls asleep but she's not doing it as much anymore. When you said his arms get all stiff do you mean it looks like he's balling his fists, holding his breath and then screaming? My daughter does that every so often.. I thought it was a temper lol but realized it wasn't.

Both of my children were very sensitive to being laid down also.
They did exactly what you are describing if I wasn't holding them.
I used an infant sleep positioner to snug them in when I wasn't holding them or changing a diaper, etc when I was at home.
If I was out, I'd use a rolled up baby blanket placed by their side to give them the sensation of something pressing against their body when I was changing their diapers.
I swaddled my children a lot too with receiving blankets (like they did in the hospital) and that really worked good too, just open up the bottom of it and leave it wrapped around the arms when changing a diaper.
Just a few thing for you to try if you'd like.
They seemed to help my children feel more secure.

My son does this as well! Right now he's 11 weeks old and has been doing this since he was about 7 weeks old. We noticed it when we would place him on the changing table and he would usually be fussy because he didn't like his diaper changed. When he got really upset, he would throw his arms out to the side and kind of "move" from side to side as if he was trying to catch himself from falling. At the same time he'd do these short cries but they sounded like he was terrified. He would do this until we picked him up or until we placed our hand on his little body and talked to him.

He also did this in the crib and when he's in his bouncy chair and the swing. Mostly when he's on a flat surface. Lately, he's been waking himself out of sleep doing this, which concerns us even more.

We asked our Dr. about it (even video recorded him doing it and showed her) and she said it was normal as long as he can be consoled from picking him up. He's still doing this and it never fails to scare us because he sounds like he's just terrified... and it does seem like he thinks he's falling. We're trying to swaddle him more, which he's not exactly crazy about because he likes his arms free now, but we're keeping him swaddled at least the first part of the night.

I'm hoping he will grow out of this and I will take some of the suggestions I've read (especially from automansgirl) and see how this works. Please report back on how your son is doing. Best of luck. I'm sure this will pass. ;)

My 2 oldest kids were the same way, we used the bed or couch.

They hated the chaging table unless my wife and I doubleteamed the task.
One would occupy the babies attention while the other changed the diaper.