1999 Mercedes-Benz M-Class - Hard cranking

For the last year, my starter would, off and on, take longer to crank over the engine. Normally it would start immediately once I turn to start and let go, but there are times it would crank a few seconds longer than normal. Hot days are even worse. It will crank until it cycles out (5-10 seconds). Sometimes I have to go through two separate starts and a panic attack before the engine turns over. I know it’s not an problem with my battery, and I have the vehicle serviced regularly. When I bring the issue up to my mechanic, it never acts up ( Murphy’s Law).
Will I have to wait until it completely quits, wait hours to be towed and explain to my wife why I was late, before it can be diagnosed?
I have a service dog (German Shepard of course) that goes everywhere with me and I don’t want him to be stuck in a hot vehicle with no air conditioning.

That is the sign of a failing fuel pump and not a starter issue.Since your vehicule is 20 year old,almost anything can go wrong depending on how well the car was maintained.Have the mechanic test the fuel pressure.

Thank you. Fuel pump replaced 10/14, but I’ll have the pressure checked on the fuel pump anyways.