When you go to Heaven are you alive?

In Christian belief, the body returns to the dust of the earth while the spirit in man returns to God for safekeeping until the call of the resurrection to Judgement before Christ - when the spirit will be placed in a new body, physically alive again:

New King James Version (NKJV)

Then the dust will return to the earth as it was,

And the spirit will return to God who gave it.