96 safari starting problems

I have been inconsistent problems with the van starting. The first time I turned the key to start, there was no noise from the solenoid or starter, and nothing happened. Checked the battery, tested ok. Put it back in, at the same time, took starter out and jumped with wire from the battery, starter worked. Put back in, fired right up. So I was waiting to drive it, and weeks later, fired it up and flushed the radiator, the whole time van started and ran great. Parked it for a day, got in to start, turned key and nothing. Got pissed, drove my truck. Next day, fired right up. Keep checking and keeps starting. What causes inconsistent starting like this? Bad connection somewhere? Would like to start driving since mileage is better than my truck and easier to get kids in and out. Please help. Can't drive unless starts all the time.

clean the battery connections and also the engine ground end of the neg cable. a quick check for bad grounds is to check for voltage in your coolant. with a cold engine start it up, take off the raditor cap and test with a volt meter by putting the postive lead into the antifreeze and the neg lead to a good chassis ground. voltage in the coolant should never be more than .03 volts.