Is it normal for a man to not want a girlfriend?

I just started to date a man who is 48, I am 49. He told me the first days that I was beautiful and asked me over and over if I would be his girlfriend. I said I would and I really like him. But then he changed and said he doesn't want a girlfriend, just a casual thing, and he told me the longest he ever had a girlfriend was 3 months. He acted all moody, but apologized the next day and said he would see me again next week. I told him I would see him casually, but not once in a while, but every week or so. I guess I have to wait until I see him again. He might have mental issues because of how he changed. I also know he had a cold and didn't get enough sleep and had to work when he said that. But he was also very nice when he wasn't moody. It is very confusing.