You have a shorting membrane keypad. And you are correct - if and when an oven is coming on or doing anything by itself, this is very dangerous and can result in a fire.
So until it is repaired, please leave it unplugged or leave the door open when it's not in use, and of course one should
never leave a microwave unattended while cooking, especially if it's doing this!
The details of my answer assume that your model number (from the tag on the microwave, not the manual) is FFMV162LWA (white). If not, please let
me know.
On these models, the membrane keypad is not available as a separate part, so you would have to order the
control panel frame assembly which comes with a new keypad.
In this case, you simply move your circuit board into the new frame. That is a simple do-it-yourself job.
You can order part number 5304477374 from the
Sears Parts Direct Web site for $98.65 (prices subject to change).
There is a video
here showing how to remove a typical over the range control panel assembly in under 5 minutes.
Then detach the keypad connector as shown in the photo below, and then remove the control panel screws.
Be careful not to crack the glass display when handling it, or it's a goner.
Some connectors have a lock.
Reassembly is the reverse of disassembly.