Use a cut-off valve for the shower like this one:
Shower cut off valve - Save Water - Be Green | greatgreengadgets.com
That way, you're not wasting your precious hot water by having it run down the drain while you're soaping up, and you won't also have to fiddle with the water to get the right temperature when you turn it back on.
If your water heater is tripping the dryer, you've definitely got a problem.