Switching on/off issues?

A few months ago my 11" MacBook Air power button stopped working when switching off, and so I am having to use the Apple () menu from the upper-left menu bar and then choosing shut down, but it didn't seem to have any problems turning on. However, recently, I was using it as usual, and the screen went dark and a message appeared on the screen saying that I needed to restart my computer. This caused a problem because I couldn't switch it off because my power button doesn't work and it wouldn't let me use the menu, so I had to wait until the battery died. Since then everytime I switch the MacBook on I'm having to take the power adapter out for the power button to work, and it doesn't respond to pressing the power button when it's plugged in.

It's not a major issue, but I'm concerned that I might have to reset the SMC or something along those lines so that it gets back to normal. Thanks.