Hydraulic out of prime

If my tractor sets for more than 3 days, the M110x tractor needs to run for 15 - 30 seconds before the hydraulics kick in. The sound of the pump actually changes. It was -5 degrees last week and it took 60 seconds for the hydraulics to kick in. Almost acts like it bleeds down, that the pump is not primed. The dealer changed filters/fluid before I purchased it. It has 3000 hours on the machine. Has anyone come across this? Not sure if this is something to be concerned about.

It could be normal or it could be that it has a suction side leak allowing air to get sucked into the system.

Sounds good. Thanks for the info. This is the first tractor I have owned that is less than 40 years old so still figuring out the quirks. I am a bit paranoid that I will break it before I get it paid for. Only 64 more easy payments to go! Thanks again.