Macbook is extremely slow and goes into overdrive when nothing is open

Question

Starting a few weeks ago my MacBook has been acting strange. A few times it will go to sleep, and I am unable to wake it up again. Now, even after running Disc Repair and restarting my computer everything takes a really long time to load (like a few minutes to switch between applications) and the internet is even slow to load (and on my iPhone my connection for internet is just fine). My computer has also been going into overdrive a lot even if I don't have anything open. This is seriously affecting my school work as it takes me 5x as long to do ANYTHING on it. Any suggestions?

Answer 1

By 'overdrive', I assume that you mean the internal fan is running at high speed. You didn't mention the 'spinning beachball'. Does that also show up frequently when you try to switch applications?
Both are symptom of the CPU working at a high % of utilization, and that is often caused by an out-of-control application program process or 'stuck' print job.
1. With no applications running after restarting your computer, open Activity Monitor, view All Processes, and click on the % CPU column to sort programs running in Highest to Lowest CPU activity. If you have any process using more than about 15% CPU momentarily, or anything showing in red as 'Not Responding', you should Force Quit the process, and restart the computer. Check again to see if there is anything else using a high % CPU. Viewing Flash Video on a web page, such as YouTube often causes my fan to come on and CPU utilization to exceed 25% (I've got an older Core2Duo MacBook.)
2. Do you use the computer on a soft surface such as a blanket or pillow? That can restrict airflow. If the computer is used in a dusty environment, maybe there is a significant accumulation of dust & dirt inside the case that is restricting the fan and/or airflow.
3. Check free space on your hard disk. (About This Mac, More Info, Serial-ATA) Less than 15% free (e.g. less than 18Gb free on a 120Gb drive) is likely to cause slow system performance as the hard drive has to keep looking for free space.
4. How much RAM memory do you have? (About This Mac) If you have 1Gb or less, more RAM will increase apparent performance because processes will not have to write memory contents to hard disk, such as when switching applications. But unless one memory stick has recently gone bad (which should generate a Kernel Panic screen) you're not going to notice a SUDDEN decrease in system performance.
5. Have you loaded recent Apple software updates? Have you searched Apple Discussions for other 'slow performance' threads for your computer model? I've taken to waiting weeks or longer before installing the latest Apple updates after checking the forums to be sure that any issues reported do not affect my MacBook model and OS combination.