1997 Toyota Camry using instant starting fluid

I have a 1997 toyota camry, and every time it's rainy and humid, or rainy and cold, much like it was today, the engine will rotate but will either not start the first time, or start sluggishly. This time it just would not start at all. A mechanic recently told me that sometimes oil can get into the belt and hoses, and obstruct the flow of air. I would like to know what parts of any, I should consider replacing, and how to use the starting fluid.

Thanks