I have a long time problem for about a year now, which is when I try and put in into 1st gear it is hard and have to force it in. But if I go into 2nd gear first and then into 1st its a lot easier.
On a cold vehicle that's not uncommon. I have to do that myself regularly. If your mileage is high, then you might want to try changing your transmission fluid, but it would have to be very high like over 100k.