VW Golf hot weather problem

I have a 93 VW GOLF with only 55,000 miles on it. When the weather gets warm I have trouble starting the car. Sometimes it won’t crank, sometimes it cranks, but doesn’t turn over. So far, it eventually starts, but may take a number of tries. Today I had to sit for almost half hour before it finally turned over. Any ideas?

When it does crank but does not start, is it turning over at the normal speed?

How old is the battery? Have the cables been checked? How about the batter and charging system? Many places will check them for free.