I have a 2007 Maxima and when cold starts or in the morning my steering is hard to turn, once the car is moving under normal conditions it is find, I had belts replaced a few months ago because of squealing, the hard steering has been going on for a year, no leaking

 

Power steering fluid may be contaminated. Water or just gunk. Ideally just having the fluid flushed out and replaced could solve your problem. Could also be a bad pump, which replacing the pump will get you fresh fluid too...

 

More than likely you have a bad high pressure hose, common for these vehicles. Does your car leak any fluids? Check the fluid level and make sure its topped off of if not add some. Keep an eye on fluid levels if it keeps running low check for leaks. Mine did this too when cold, replaced the high pressure line now no more issues.