M.O.
Hi Wendolyn,
I agree with a lot of what Renee said.
A 3.5-year-old ought to be able to understand the idea of "wrestle time / not wrestle time." In other words, my recommendation is to set aside a little time when your baby is napping, when you're wearing something that's already baggy, when you can just roll around on the floor and help him get his energy out. If you really HAVE those times with him, it might be easier for you to say "it's not wrestle time now" under other circumstances.
For other times, what about getting him a big stuffed animal (you know, those ones that are the size of a preschooler) that can be his "wrestle buddy"? Sort of a preschool version of a punching bag.
And ... as I'm sure you know, life will probably get a lot easier in about a week, when the weather warms up. Kids have so much less pent-up energy when they can run around and play outside.
Best of luck,
Mira