turn key starts, turn off truck nothing, wait 20 min and starts

So have a little problem with our Suburban
sometimes you turn the key and it wouldn't
start sometimes it would start when it starts
to drive it somewhere turn it off it won't start
again for about 20 minutes we took it to a
garage about a hundred twenty miles away
from our town this town has two garages
and to dealerships so we called one of the
dealerships and they said that they could see
us we get there and they were full, but they
did a little Diagnostics and said we should
go get stuff checked at Napa do a little
check have them bring out the machines
check this battery, starter, they plug their
little thing in and read the codes, when they
plugged in their reader, one was a code
about key ignition security something they
tested the starter tested the battery
everything was good battery was a little low
but not critical so we took it to the other
dealership but we called them bright and
early at 7 in the morning and we told them
our problems in our issues and told him that
if we bring it to you guys you can't turn it off
and I have two little baby boys in the back
seat relive 120 miles away so if you can't you
do a Diagnostics and you can't figure out the
problem then we need to move on ladies
front desk told me that they rarely ever have
to send someone away so just bring it in will
be fine so we bring it in pulling into their
shop and he turns it off and I said I just told
you but we need to know what's going on
before we just shut it off cuz now what are
we going to do so we decided we are going
to take the boys and take a cab and go to
Walmart give them a few hours to diagnose
it and call us and let us know what the
problem is or if they can fix it what the deal
was they're being very secretive and asked
us what our budget is while they were under
the hood before they even found anything
out open the hood not so what's your budget
then he starts unplugging relays and moving
them around and testing things that we've
already tested out so we decided to just go
to Walmart for a few hours 4 hours later we
don't get no phone call no nothing so my
wife just said she's going to call them and
find out what the deal was the lady at the
front desk said they can't figure it out the
cars stuck in their Bay and they have other
trucks they got to move in so we need to
come pick it up and that the mechanics all
went to lunch half an hour ago they said it
was ECM problem I would take some a
couple weeks to get the part in they're going
to charge us $1,000 to put the part in and
order it we show up there and they try to
charge us like three hundred bucks in my
wife throws a fit and they tell us that they're
only going to charge us for one hour of
Diagnostics I got to call a tow truck and have
them pull it out of their Bay find a parking lot
to park it in for a couple weeks until I can get
more money too fix it after all that was said
and done come out to the house later we
ordered the ECM at a hundred and fifty bucks
supposed to be pre-programmed we went
down to the car put a brand new battery in
put a new ECM in and it fired right up turned
it off and I didn't start again so we towed it to
the dealership left it there for 4 days we got
a call from them saying that it was fixed and
running 250 bucks went down there picked it
up everything look good got it home turned it
off and same problem so the problem is
when you turn the key on lights come on
door dings but you get nothing turn it back
nothing turn it back nothing turn it back
nothing and then it will start had to drive it
had an emergency power stuck in Salt Lake
start it up yesterday we drove it here now it
won't start can you turn the key you can hear
everything clicking it can hear all the like the
fuel pump trying to go