It's intimidating we are scared our partners will not reciprocate so who say "I love you" first. Psychology today, men are more likely to say " I love you" first, some men say it after dating of a few weeks, why are men in a hurry.
firstly, Women need more time to assess a man's value as a mate
secondly, some men say "I love you" as means to an end (sex). Men say "I love you" before having sex for the first time, the objective is to gain a partner's trust. It's risky for a man say it too early because women will pick up on the strategy. Women prefer to hear it after having sex for the first time but it's not all about sex, men say it first because they think they are supposed to take the lead.
If you are going to say it, make sure you mean it
finally, last thing I would to say " te quiero"