You have this feeling your co-worker is interested in you. His body language makes you feel he wants to date you. Every time you look his way he is checking you out. He seems to adjust his tie each time he is in front of you. Look for him to find reasons to be around you. Listen for other co-workers to make comments about his special treatment toward you. Keep the conversation between you light until you are sure he is interested in dating you.
Look for signs of interest, she might start hanging around your work area or ask your opinion about something just to start a conversation. She might talk loudly to other co-workers just to get your attention.
Find ways to avoid him and see if he stays away. Change your lunch time and see if he changes his lunch time, too. Leave later than usual, if he is waiting around in the car park, he might be interested in dating you.
Listen for office gossip. If she is interested in dating you, she might have shared that information with another co-worker. Talk with mutual office friends and see if she might have shared her interest in wanting to date you.
Go out with co-workers and see if he shows up. Look for him to find a reason to be close to you. He might sit in a seat that is open next to you. Ignore him and talk with other co-workers, then notice if he invites himself into the conversation.
Notice the body language your co-worker might send you. She might touch her hair or glance your way from time to time. He might stick out his chest or walk by you to get your attention. A smile from a distance can send a non-verbal message that your co-worker in interested in dating you.
To avoid embarrassment, keep your suspicions to yourself until you are actually asked out on a date.