This question comes up (everywhere) fairly often.
No, you are not too old.
Will you be older than most rookies? Yeah, you will.
Are you too old to start at some agencies? Yeah, you are (35 is a hard line in a number of places, some are higher)
The thing you need to ask yourself is, are you up to it?
Some agencies have a fair operational tempo. You will take a lot of hot calls. Jumping fences, kicking doors, fighting with fools. Are you up to that?
Some agencies are pretty slow...but you never know when it will go down, will you be ready?
Good luck. There are people in there 50's who start this game.
In the world to come, each of us will be called to account for all the good things G-d put on earth which we refused to enjoy. ~ The Babylonian Talmud
Whenever you get mad as hell about it all, grab your rifle and head outside. If you are the only one there...it's not time yet
"Few men desire liberty; most men wish only for a just master." - Sallust