Disappearing icons is usually associated with an incomplete install. You can try this and you may need to reboot more than once. The result should get better as you go. Reboot the computer whilst holding down the shift key. That will force a full reboot. It will take longer than usual and you may need to do this twice but it should fix itself.
If this is a laptop, make sure you are on a hard surface that won't block the fan vents and cause overheating.
If this fails you will probably be having a ram, hard drive or processor issue. For you to be posting this it is probably best to take the box (computer) to a repairer or a knowledgeable friend.