What exactly is the problem that you're experiencing with your starter? Is there a single click or cloak when you go to the start position? Or are you getting a worring or grinding sound when the starter is engaged?
This is a very well-known problem on the 89 and 90 Camry and Celica 2.2 L engine. What is happening is the starter is prematurely spinning before it is engaged into the flywheel. Over a period of time it grinds the teeth down on the flywheel. The reason why it does it sometimes and not others is because the engine generally stops in one of four places because of the compression cycles. Unfortunately in order to repair this correctly you will need to replace the flywheel and the starter that has the new update drive and solenoid. If you try and put a new Bendix drive into the starter it will not solve your problem. If money is tight and you cannot afford to replace the flywheel because the transmission will have to be removed you can try a new or remanufactured starter and it may make up the difference the teeth on the flywheel are ground down but it is not likely going to solve your problem completely. Sorry to be the bearer of bad news but I have fixed many of these because of this problem.