When I first purchased my 2000 V70 from the dealer as a Volvo certified used car I took the car home and realized immediately that there was an intermittent problem in starting. Sometimes I had to crank for up to 7 seconds for the car to start. This was not related to ambient temperature. I was disappointed and returned the car to the dealer. At first they replaced the Antenna ring, which made no difference. Then they hooked up a pressure gauge to the fuel system, and found a drop in pressure over time. This lead to an examination of the fuel components- fuel pump and fuel rail. It ended up that there was a leaky fuel rail, which was replaced and I have not had any problems since then. So perhaps you should have the pressure recorded in the fuel system when the car is at rest. If that is normal then perhaps it is in the ignition system. Good luck, I know how frustrating this problem can be.
BillF