If the following suggestions work, please let me know and you can Accept the answer (and if possible, leave positive feedback). If not, please DO NOT Accept the answer. Instead, let me know and we'll try some more things or I can refer you to another Expert who may be able to help you further.
First, there are a few questions I'd like you to answer so I can better help understand the problem.
1) What type of Mac (ie iMac, PowerBook, etc) and how old is it?
2) What is the Operating System (ie 9.2, 10.5.8, etc)? This info can be found in the apple menu, "About this Mac" (if it is running).
3) Have you recently installed anything new, updated the computer, upgraded OS or software? Did you start noticing the problems with Safari after a specific event took place?
4) Do you have Firefox? It's a free application, which I HIGHLY recommend. It is a more stable browser than Safari in my opinion and often runs more smoothly for most mac users. I suggest giving it a try as long as your computer meets the minimum system requirements
Back to the Safari issue, I would suggest you run some general maintenance on the computer. It is an obvious square-one approach. I normally suggest this first because it is good practice plus if we dig too deep into a problem and simple measures could have repaired it in the beginning we'll be kicking ourselves later... This is going to be a long email so I suggest printing it out for your reference.
First let's reset the PRAM on the computer.
1) Shut down the computer.
2) While the computer is shut down, locate these keys: command (has an apple on it), option (sometimes called alt), P, and R.
3) Turn the computer on, then press and hold Command-Option-P-R before the gray screen appears.
4) Hold these keys down until you hear the startup sound a total of 3 times.
5) Release the keys.
Next, let's try a Safe Boot. This will perform several clean up procedures that may be affecting the machine's performance and startup.
1) Shut down your computer completely.
2) Start up the computer and immediately after the startup chime, press and hold the Shift key
3) Once the gray Apple and progress indicator appear, release the Shift key
4) Note: Startup will likely take substantially longer than normal
5) In Mac OS 10.4 or later, you will have to login to your account, even if it normally does so automatically.
6) Shut down the computer.
Now let's check / repair the disk permissions. Although this doesn't fix all problems it is a great way to start when working on a machine, besides it often cleans up any other smaller problems you may or may not be experiencing.
1) Restart the machine.
2) Before you have opened any programs, go to Applications / Utilities / Disk Utilities.
3) Run the Verify Permissions, then Repair any errors it finds.
4) Shut down the computer.
5) Restart your computer, how is Safari operating now?
What version of Safari are you using? This can be found in the Safari menu (about Safari) if/when the program is running.