the semi-auto 357 coonan offered a special 38 caliber strength recoil spring so you could do exactly that, but the gun is pretty expensive and I don't know what the reliability was.
The Desert Eagle is the other 357 semi-auto and I think because of the gas operation system you HAVE to have the 357 for the slide to function. You might be able to use 38 jacketed +p bullets, but I'm sure you'd void any warranty and if you're going to pay for 38+p jacketed, you might as well buy generic 357, it'll be cheaper.
Now if you are REALLY confused, and thinking about shooting 38's in a .357 semi-auto that is chambered in .357 SIG then NO, you can't do it because the cartridges are totally different even though the number is the same.