Is the risk of eating pepperoni pizza from restaurant high for food poisioning?

Not. Usually but cold cuts do cause risks in immune compromised individuals but overall eat that pizza.
Food poisoning risks. As a general rule, food that has been cooked and has steam coming off of it is 'safe' - since few germs can survive heat like that. Foods that are washed (or not washed!) and eaten raw or undercooked have higher risk. Think of salads or the undercooked hamburger in summertime. An ID doc may be able to nail down the cause with a good food history & accounting of symptoms. This pizza is innocent!