Just purchased 2004 G35; car was running fine. Same day we purchased, however, car needed to cool off a bit before starting again, if turned off. we've changed spark plugs, crankshaft sensor, and fuel pump. We've put on computer analysis but cannot figure out why car must cool off (or at least sit for a bit) before restarting. Any ideas?

No codes? If codes pop up you can refer to the FSM for resolution.