Usually implies disapproval. It's often about unwelcome actions or ideas in social contexts. He tends to obtrude his advice even when not asked.
Pro Tip 2/3
Non-physical Intrusion
Often used for metaphorical rather than physical impositions, like thoughts or feelings. Her doubts obtruded upon her happiness.
Pro Tip 3/3
Cultural Intrusiveness
Think of obtrude as intruding in cultural situations like conversations or personal space. He didn't realize his comments would obtrude on her privacy.