transport won't start

I have a 94 transport 3800. A couple of months ago, it would start, but when I stopped for gas or to the store and try to start it again, it wouldn't do anything, it just totally went like battery dead. What used to work to get power back on was I would kinda move the battery cables around and I would get power back on. I changed the cable but the problem persisted. Took it to a mechanic and he said it was alternator problem. I had that changed. But the problem didn't go away. Only this time, I can't get it back to life by moving the battery cables at all. But if I leave it for a couple of days and start it, it would start good.

I took it to the mechanic, he said the water pump was bad, had that replaced and had all spark plugs and cables replaced. Car ran fine .... for ONE day!!! The next day, it went dead again. No amount of shaking cables could bring it to life this time and it's been sitting in the driveway for 3 weeks now. It's like battery dead.

I am real sick of this problem. :banghead: I have since bought a Honda Odysey and hoping to fix this problem to sell the Pontiac. Anybody has any ideas? At least to get it started so I could send it to the mechanic. Would save towing charges :lol:

What you did not mention is if there were other electrical accessories still working. NOT CRANKING AT ALL on a sudden and coming back to life (for a while) when moving cables is generally battery connectors, or battery connectors and finally, battery connectors. Often, one will change battery and all will come back to life just because cable connectors have been displaced and corrosion has cracked away someway, and the old battery was still in working order anyway.
If you have not scraped and scraped cable connector and battery terminals to bare shining metal , give it another try and insist: lead corrosion can seem hard and metal like, but I have had 1/8 thick washer like cushion between cable connector and battery connector...
THere might be starter problems, or starter cable problems but then other electrical components will work EVEN WHEN TRYING to start. With faulty battery connectors, all acceessories and lights will go dead when trying to start, even if they were alive before starting.