There are many signs both physical and mental that you are close to shifting realities.
Here are some that I have had and I've commonly heard other people have experienced. (Let me know if there's a symptom you get that I didn't list here.)
Seeing a bright light
Objects or people forming
Hearing, seeing, or smelling something different (or specific to your dr)
Feeling outside of your physical body
Forgetting where you are
Tingles
Feeling detached from your CR
Feeling very calm
Subliminal/music fading away
Hearing ringing
Feeling distant from your current reality
Feeling like a different person/something had changed within you
Twitching
Change in temperature
Numbness
Elevated heart rate
Feeling like you are floating or falling
Minor Shaking
Strong urge to move or get up
Dizziness
Lightheadedness
Swirly feeling/feeling like everything is spinning
Feeling as if someone is touching you or pushing you
Headache
Angel Numbers/environmental signs
Angel numbers, (111, 222, 333, 444, 555, NOT 666...) are numbers that are known to be lucky and have positive energy. They each have different meanings. (There's plenty about it on amino, for example 111 or 1111 represents manifestation, and that your message has been received.) Seeing them throughout the day or at all are signs that you positive energy is high, meaning that you will shift soon!
An environmental sign is a feeling, or sign, that you just know you will shift soon. For example, I love the rain. It helps me sleep. Last night, I was starting to lose motivation and confidence. Right before bed I decided that I would not try to shift because I didn't feel comfortable or have motivation. Just seconds later, it started raining. Suddenly I felt a jolt of inspiration go through me and I felt like I had to shift! This can also be: feeling randomly happy or confident, seeing things from your DR in your CR, things going your way more than usual, having lots of motivation, etc.
Breaks
While attempting to shift it is also very important to give yourself breaks! It takes a lot of energy to shift. Taking breaks will not set you back in your journey of shifting, it will most likely help!