How to disable the character accent menu in El Capitan

Thank you for answering the first part of my question. Do you have any suggestions to stop the bizarre behavior?

My computer is acting very strangely as if it had a "life of its own!" What has been happening (and what I've been on the phone for hours with Apple Support) is that sometimes (intermittently) when I type a letter (usually an "e") a bubble comes up foreign letters with accents, etc. and then the computer continues to type this letter; then erases it; won't enter what I type and finally, I have to reboot the machine to stop the bizarre behavior.

I'm hoping if this feature is disabled that the "possessed" entry of characters and then erasing them with a sound in the background will stop occurring. The only way I can take control of the machine after this bizarre behavior starts is to reboot the computer.

Does anybody have an idea of why my machine is acting this way and what I can do to stop it.

Mr Hoffman,

Thank you, I had posted earlier about installing some MacPaw software and you made various suggestions which the Apple Tech and I have tried. Thursday, I took the iMac to the Apple Genius Bar and had a hardware scanner look for any malfunctions; it came back negative and said everything was fine. Then I had the hard drive erased and repartitioned and a "clean" copy of El Capitan was installed. When I came back home the Apple Tech had me install programs from the backup (Time Machine) individually and I only put back Office for Mac 3rd party software (after reinstalling my user profile). This is what you had advised but unfortunately the problem is still there.

If I hold a key down too long the pop up bubble menu with the foreign letters accented comes up; usually, I just delete and things are fine. HOWEVER, when the machine is acting up with bizarre behavior, letters are typed in while I'm watching the screen then they're erased all the while hearing a background noise of ticking or typing. The machine will not input what I type anymore and the only thing I can do is to reboot the machine.

Another user is having the same problem:

My iMac has recently developed an intermittent fault when using the keyboard

for typing. When it occurs it takes several seconds to put each character on the

screen and options for the letter typed are offered (see screenshot below).

Typing beyond the letter in question and the system goes haywire with no

response to what was actually typed and there is a background beeping as

thought the system is trying to catchup, other keyboard commands such as

backspace are also mis interpreted. I can't identify any particular trigger for the

problem, a virus checker is showing no virus and a reboot corrects the problem.

Answers to your other questions:

It is a Blue tooth keyboard and mouse that came with the iMac. I have an older iMac in my basement that uses the same setup so we tried "swapping" the peripherals but still have problem. I have asked the tech if he could loan me a USB wired keyboard but no answer yet. No antivirus or malware programs and I already told you the other 3rd party programs were removed with the clean install. Haven't tried looking at console yet for repeating blocks but I will look at it (not sure I'll be able to decipher it though). Tech said we may try creating a new user via system preferences so we'll see later if that helps.