Heat-Related Starting Trouble

My car doesnt like starting when it’s been sitting in the sun. It’s been going on for a while but I ignored it because winter temps set in and problem went away. I don’t have the problem in the shade, cold weather, or in the morning.

When attempting to start, it makes a strained noise, sound comes from steering column, not under hood. It almost sounds static-y, like a car version of the old dial-up internet connection noise. If the outside temp is around 80, it usually whines and turns over after about a few minutes. If it’s 85+, it won’t start at all (but make the weird static noise).

Mechanic tested battery and alternator, said both are fine. Mechanic wants to replace starter, but I asked around and NO ONE has ever heard of temperature-related starter problems.

Friends have suggested main relay, battery, and fuel pump.