1998 Nissan Altima 98 Nissan Altima shakes

Your car may be equipped with an Air Conditioning Idle Valve which increases idle speed when the air conditioning compressor engages to compensate for the greater power required to run it. If the A/C Idle Valve is not functioning properly and switching on, then the A/C compressor needs more rpms than your motor is producing at standard idle, and pulling power from the engine itself.
Other possible causes are poor fuel pressure. Replace fuel filter first. Doesn't solve problem check fuel pressure. Your fuel pump may be bad. Spark may be weak, check for healthy blue spark at plugs.