"Get one of those small, oil filled heaters from Bed, Bath, and Beyond."
Triple recommendation.
I had one I bought second hand in 1992. I used it every winter in my bedroom until last year when the low setting toggle switch broke.
I have two others that I've bought more recently.
I have no problems plugging them in and letting them on while I am sleeping.
If you are going to use an electric heater, these are probably the safest and most foolproof.
Don't, however, just plug it in and assume that everything will be peachy for 4 months. If something does happen, you could end up with real problems.