Chosen Solution
My iMac is about five years old and it keep giving me the spinning rainbow wheel between screens and if I have too many things open. I have backed up most of my stuff on an external hard drive.
Don’t open too many things. Seriously you might try adding RAM or use the HardWare Test disk to check your HD. If this Answer is helpful please remember to return and mark it Accepted.
If the spinning wheel bothers you too much and this began to happen these days, and not used to before, there are plenty of reasons for such. Before thinking and spending bucks for upgrading any parts, look into some soft issues first. Go to System Preferences, Users and Login Items. Remove all items from there. Restart your computer and see if that improved the spinning wheel behavior. If not, reset your PRAM. In this case, turn off your computer, turn on, press Command, Option, P, R keys at the same time. When you hear another chime after you pressed those keys, release the keys and let it boot up normally. If that didn’t solve the issue of your spinning wheel, create a new Admin account and log in to that new Admin account and see if you observe the same spinning wheel behavior. After attempting these soft solutions, if still the same issue persists, upgrade your RAM. That should improve speed performance slightly by decreasing the spinning wheel behavior. Enjoy!
I cleared the login items on both accounts and the mac is way better than before, Very grateful for the advice. Kind regards Bruno.