If you are able to get an erection, then there are no physical problems. Arousal can be affected by performance anxiety, and without arousal, it is difficult to get erect. The problem with performance anxiety is that it is a self-fulfilling prophecy. The more you worry about your performance, the less likely you are to perform. And when you don't perform, it puts more pressure on you to perform the next time. This then forms a negative, vicious cycle of performance anxiety, and then you start to dread the activity you desperately want to succeed.
I would recommend taking some of the pressure off by just having fun with your wife, without sex. Try going on dates, and go on fun activities together- hiking, swimming, long walks. My wife and I pretend we are in a faraway, cosmopolitan city when we go downtown in our own city. We act like we are tourists and check out all the tourist destinations that we otherwise would ignore in our own city. Then we pretend we are going back to our hotel room at our house, and place the kids with babysitters.
Also, it would be good to have a frank discussion with your wife about your arousal problem. If you are honest with her, she may be understanding and she may be less likely to feel rejected if she knows what the problem is. And if she is understanding, then you are less likely to feel the pressure of performing.
So just try to relax and enjoy time with your wife, without the expectation of sex. When you start to connect with your wife intimately through dates and fun excursions, then the sexual attraction and arousal will come naturally. Just don't focus on it for now- just have fun with your wife.