2005 Chevy Tahoe Starting

Are the battery cables/wires clean and tight on both ends? When the problem occurs, have you tried cranking it in neutral? You could do some testing at the starter relay.

Can you tell if there is a load on the starter circuit, when the problem occurs? If there is a load on the circuit when you turn the key to crank, the dash lites--dome lite-- headlites may dim. If all the lites stay bright, there may be an open circuit.

You have to do the testing when the problem occurs. When you turn the key to crank and there is no starter action, the lites dim, a little? Or do they go out?

When it refuses to crank, can you check for voltage at the starter field terminal? That circuit goes from the lower part of solenoid into the starter housing. When the starter refuses to crank, if there is good voltage there and your sure the grounds are good, then you may have a starter problem.