According to Michael Press :

The master bathroom in my house is freezing in winter. I'm thinking
of installing a wall heater or portable heater that I could put on a
timer to run just for a couple of hours in the morning. I have 2
options:

1) Install an electric wall heater. There's an outlet on the other
side of the wall in where I'd install the heater, so I could run power
to it easily. The heater would be 2ft from the toilet, 4-5ft from the
shower and 6ft from the bath. It would be in a corner, almost under a
window (the window's on the other wall formed by the corner).

2) Install an outlet, presumably a GFI, in the same location, and plug
in a portable heater on a timer.

Any opinions? Are there any electrical code issues I should know
about?

Code doesn't like electrical outlets or switches within 4' (or so,
details vary from code-to-code) from a shower or bath. This would
apply for a permanently installed heater too. I don't think they care
about toilets.

While code doesn't rule on how close a portable heater can be
to a shower or bath, it's best to follow it anyway. Make sure the
cord ain't long enough for it to fall into the bath...

It must be on a GFCI regardless (tho a permanently installed heater
may be code exempt if you want to be picky).

Under a window is best for efficiency.

I'd prefer a permanently installed one.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.