Subaru Outback starting Issues

My 2014 Subaru Outback has had some starting issues ever since I bought it used. At first I thought nothing of it, but now it bothers me and has gotten worse. It currently has 106k miles on it. When I turn the key, it’s slow to start and sometimes makes a grinding sound, but it starts after no more than 5 seconds. Once my car is warmed up though, I can usually turn it off and start it again no problem. I just got a new battery and spark plugs, and I havnt noticed the lights dimming - although my passenger side window is slow to roll up and down…

I asked my mechanic about it and he said it was most likely the battery because It was on the lower end of juice. New batter didn’t fix the problem… could this be a starter issue or possibly an alternator issue? If so why has it lasted over a year?

Have someone look at the starter.