I bought a used car recently and it experienced 2 incidents of stalling when I came to a stop. It restarted easily and otherwise seemed OK. In checking this out the mechanic showed me a very dirty air filter. We replaced the filter and he performed a clean out of the air induction system which he said was dirty also. No more stalling.
A very dirty air filter will restrict the air flow into your motor. The amount of air needed so the gas and air are mixed together in the proper fuel/air mix ratio is huge, especially when you accelerate and at high speeds. If the filter is really dirty and you don’t get enough air flow here are some performance issues you may notice; stalling, poor acceleration, stumbling when you press on the gas, fouled spark plugs, carbon build up, less gas mileage.
Follow the mfg recommended replacement schedule. If you drive frequently on dirt roads, dusty roads (in snow country that is the stuff they throw on the roads in snow storms), tow a trailer frequently; in these cases change more frequently. Say 1/2 to 2/3 of the normal replacement schedule. If you have a Toyota they go with 30,000 for most of their vehicles as normal replacement.