While it is normal it isn't easy! I worked in a gym child care for 13 years and its so hard on the parents and employees when a little one doesn't like it. Now that I have my own kids I realize how hard it actually is on those parents.
Your best bet is to start by taking him in and playing with him, maybe 10-20 minutes and then start to move away from him while he is playing but stay in the room. Then start leaving the room and you can even get a few minutes workout by this time (you should be able to) It may take a long time for him to get used to the new surroundings but he will eventually get that its ok.
Also, get him to know the people that work there the hours you are going to workout. At the gym I now go to there is one employee who happens to be the manager in the child care that my 1yo always goes to but he will fuss a bit when she isn't there.
It takes time but its worth it! Also try to be ready to get your workout in ASAP when you drop him off-have your workout gear on and even warm-up at home or while your in the child care just so you can dive right in and make the most of the time you do get in the beginning.
Another thought is that if you tend to only go once a week or you go every day for a week and then don't go back for two weeks you may have to deal with the same issues over and over again. You'll need to work it into his routine to keep things running smooth. Just like bedtime!
Good Luck and don't give up! You can do it!