1.
If you creep up on someone, you move slowly closer to them without being seen by them.
They’ll creep up on you while you’re asleep.
PHRASAL VERB : V P P n
2.
If a feeling or state creeps up on you, you hardly notice that it is beginning to affect you or happen to you.
The desire to be a mother may creep up on you unexpectedly.
PHRASAL VERB : V P P n